Trial Outcomes & Findings for Does Motivational Interviewing Improve Behavioral Weight Loss Outcomes for Obesity? (NCT NCT02649634)

NCT ID: NCT02649634

Last Updated: 2017-03-20

Results Overview

Weight was measured to the nearest 0.1 kg using a balance beam scale

• Recruitment status: COMPLETED
• Study phase: NA
• Target enrollment: 135 participants
• Primary outcome timeframe: Mean weight recorded at the end of the behavioural weight loss program (week 12)
• Results posted on: 2017-03-20

Participant Flow

Participant milestones

Measure	Motivational Interviewing Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Overall Study STARTED	69	66
Overall Study COMPLETED	66	60
Overall Study NOT COMPLETED	3	6

Reasons for withdrawal

Measure	Motivational Interviewing Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Overall Study Withdrawal by Subject	3	5
Overall Study Lost to Follow-up	0	1

Baseline Characteristics

Does Motivational Interviewing Improve Behavioral Weight Loss Outcomes for Obesity?

Baseline characteristics by cohort

Measure	Motivational Interviewing n=69 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=66 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).	Total n=135 Participants Total of all reporting groups
Age, Continuous	45.56 years STANDARD_DEVIATION 9.78 • n=93 Participants	44.67 years STANDARD_DEVIATION 12.91 • n=4 Participants	45.16 years STANDARD_DEVIATION 11.30 • n=27 Participants
Sex: Female, Male Female	52 Participants n=93 Participants	53 Participants n=4 Participants	105 Participants n=27 Participants
Sex: Female, Male Male	17 Participants n=93 Participants	13 Participants n=4 Participants	30 Participants n=27 Participants
Region of Enrollment Canada	69 participants n=93 Participants	66 participants n=4 Participants	135 participants n=27 Participants
Weight	95.11 kilograms STANDARD_DEVIATION 21.45 • n=93 Participants	90.34 kilograms STANDARD_DEVIATION 19.46 • n=4 Participants	92.78 kilograms STANDARD_DEVIATION 20.57 • n=27 Participants
BMI	33.78 kg/m^2 STANDARD_DEVIATION 5.98 • n=93 Participants	33.37 kg/m^2 STANDARD_DEVIATION 6.58 • n=4 Participants	33.58 kg/m^2 STANDARD_DEVIATION 6.26 • n=27 Participants
Physical Activity (PPAQ)	1574.46 kilocalories per week STANDARD_DEVIATION 1284.43 • n=93 Participants	1183.37 kilocalories per week STANDARD_DEVIATION 1106.95 • n=4 Participants	1384.93 kilocalories per week STANDARD_DEVIATION 1213.04 • n=27 Participants
Dietary Behaviour (DHQ) - overall score	2.90 units on a scale STANDARD_DEVIATION 0.47 • n=93 Participants	2.78 units on a scale STANDARD_DEVIATION 0.44 • n=4 Participants	2.84 units on a scale STANDARD_DEVIATION 0.46 • n=27 Participants
Blood Pressure Systolic	129 mmHg STANDARD_DEVIATION 13.52 • n=93 Participants	129 mmHg STANDARD_DEVIATION 13.46 • n=4 Participants	129 mmHg STANDARD_DEVIATION 13.44 • n=27 Participants
Blood Pressure Diastolic	78 mmHg STANDARD_DEVIATION 9.77 • n=93 Participants	78 mmHg STANDARD_DEVIATION 10.66 • n=4 Participants	78 mmHg STANDARD_DEVIATION 10.18 • n=27 Participants
Eating Disorder Symptomology (EDEQ) - global score	2.27 units on a scale STANDARD_DEVIATION 1.08 • n=93 Participants	2.34 units on a scale STANDARD_DEVIATION 0.90 • n=4 Participants	2.30 units on a scale STANDARD_DEVIATION 0.99 • n=27 Participants
Self-efficacy for Engaging in Physical Activity (ESE)	2.84 units on a scale STANDARD_DEVIATION 0.81 • n=93 Participants	2.83 units on a scale STANDARD_DEVIATION 0.88 • n=4 Participants	2.84 units on a scale STANDARD_DEVIATION 0.84 • n=27 Participants
Self-efficacy Related to Eating Patterns (WEL) - global score	121.68 units on a scale STANDARD_DEVIATION 31.63 • n=93 Participants	117.87 units on a scale STANDARD_DEVIATION 33.79 • n=4 Participants	119.82 units on a scale STANDARD_DEVIATION 32.63 • n=27 Participants

PRIMARY outcome

Timeframe: Mean weight recorded at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Weight was measured to the nearest 0.1 kg using a balance beam scale

Outcome measures

Measure	Motivational Interviewing n=64 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=65 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Weight at End of Behavioural Weight Loss Program, 12 Weeks	89.02 kilograms Standard Error .43	90.09 kilograms Standard Error .45

SECONDARY outcome

Timeframe: Mean weight 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

a digital scale (Tanita BWB-800S), which assessed weight to the nearest 0.1 kg, was used for the 6 month follow-up assessment

Outcome measures

Measure	Motivational Interviewing n=65 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=59 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Weight at 6 Month Follow up	91.26 kilograms Standard Error .42	91.59 kilograms Standard Error .45

SECONDARY outcome

Timeframe: Assessed once at the end of the behavioural weight loss program (week 12)

The mean number of missed behavioural weight loss sessions (out of 24 sessions)

Outcome measures

Measure	Motivational Interviewing n=69 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=66 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Adherence	3.71 number of group sessions Standard Deviation 4.12	4.07 number of group sessions Standard Deviation 3.60

SECONDARY outcome

Timeframe: Mean BMI at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Weight was measured to the nearest 0.1 kg using a balance beam scale, height was measured to the nearest 0.1 cm using a stadiometer at the beginning of the behavioural weight loss program. BMI was calculated as weight in Kilograms divided by height in meters squared.

Outcome measures

Measure	Motivational Interviewing n=64 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=65 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
BMI at End of Behavioural Weight Loss Program, Week 12	32.27 kg/m2 Standard Error .16	32.64 kg/m2 Standard Error .16

SECONDARY outcome

Timeframe: Mean BMI 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

A digital scale (Tanita BWB-800S), which assessed weight to the nearest 0.1 kg, was used to assess weight for the 6 month follow up assessment, and the height measured at the beginning of the behavioural weight loss program was used to calculate BMI. BMI was calculated as weight in Kilograms divided by height in meter squared.

Outcome measures

Measure	Motivational Interviewing n=65 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=59 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
BMI at 6 Month Follow up	32.96 kg/m2 Standard Error .16	33.11 kg/m2 Standard Error .16

SECONDARY outcome

Timeframe: Mean physical activity as measured by the PPAQ, at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Physical activity was measured by the Paffenbarger questionnaire (PPAQ; Paffenbarger, Wing, & Hyde, 1978). This self-report questionnaire assesses amount of activity performed during a typical week, and consists of three components: (1) stair climbing, (2) walking, and (3) sports and recreation. Participants were asked to report the frequency and duration of physical activity in the past week. Participants report the frequency and duration of physical activity in the past week. Scoring yields energy expenditure from physical activity per week (kcal/kg/week). Higher scores translate into greater energy expenditure per week (i.e.,better outcome). Range is 0 - no theoretical maximum. Highest observed score in our study was 10902 kcal/kg/week.

Outcome measures

Measure	Motivational Interviewing n=59 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=59 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Physical Activity at End of the Behavioural Weight Loss Program, Week 12	2161.80 kilocalories per week Standard Error 179.58	2211.87 kilocalories per week Standard Error 186.56

SECONDARY outcome

Timeframe: Mean physical activity as measured by the PPAQ, 1 month after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Physical activity was measured by the Paffenbarger questionnaire (PPAQ; Paffenbarger, Wing, & Hyde, 1978). This self-report questionnaire assesses amount of activity performed during a typical week, and consists of three components: (1) stair climbing, (2) walking, and (3) sports and recreation. Participants were asked to report the frequency and duration of physical activity in the past week. Participants report the frequency and duration of physical activity in the past week. Scoring yields energy expenditure from physical activity per week (kcal/kg/week). Higher scores translate into greater energy expenditure per week (i.e.,better outcome). Range is 0 - no theoretical maximum. Highest observed score in our study was 10902 kcal/kg/week.

Outcome measures

Measure	Motivational Interviewing n=59 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=52 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Physical Activity at 1 Month Follow up	2196.78 kilocalories per week Standard Error 184.44	2299.22 kilocalories per week Standard Error 191.69

SECONDARY outcome

Timeframe: Mean physical activity as measured by the PPAQ, 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Physical activity was measured by the Paffenbarger questionnaire (PPAQ; Paffenbarger, Wing, & Hyde, 1978). This self-report questionnaire assesses amount of activity performed during a typical week, and consists of three components: (1) stair climbing, (2) walking, and (3) sports and recreation. Participants were asked to report the frequency and duration of physical activity in the past week. Participants report the frequency and duration of physical activity in the past week. Scoring yields energy expenditure from physical activity per week (kcal/kg/week). Higher scores translate into greater energy expenditure per week (i.e.,better outcome). Range is 0 - no theoretical maximum. Highest observed score in our study was 10902 kcal/kg/week.

Outcome measures

Measure	Motivational Interviewing n=60 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=55 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Physical Activity at 6 Month Follow up	2060.09 kilocalories per week Standard Error 178.15	1789.34 kilocalories per week Standard Error 187.92

SECONDARY outcome

Timeframe: Mean dietary behaviour score as measured by the overall DHQ score, at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Dietary behaviour was measured by the Fat-related Dietary Habits Questionnaire (DHQ; Kristal, Shattuck, & Henry, 1990). This self-report questionnaire assesses dietary behaviours and high-fat eating patterns and consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The DHQ consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The overall summary score is the mean of all non-missing subscales scores. Responses are scored on a 4-point scale (usually, often, sometimes, rarely/never). Range of overall summary score is 1 - 4. Higher scores correspond to higher fat intakes (i.e., higher scores = worse outcome).

Outcome measures

Measure	Motivational Interviewing n=60 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=60 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Dietary Behaviour at End of the Behavioural Weight Loss Program, Week 12	2.64 overall score on DHQ Standard Error .04	2.62 overall score on DHQ Standard Error .04

SECONDARY outcome

Timeframe: Mean dietary behaviour score as measured by the overall DHQ score, 1 month after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Dietary behaviour was measured by the Fat-related Dietary Habits Questionnaire (DHQ; Kristal, Shattuck, & Henry, 1990). This self-report questionnaire assesses dietary behaviours and high-fat eating patterns and consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The DHQ consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The overall summary score is the mean of all non-missing subscales scores. Responses are scored on a 4-point scale (usually, often, sometimes, rarely/never). Range of overall summary score is 1 - 4. Higher scores correspond to higher fat intakes (i.e., higher scores = worse outcome).

Outcome measures

Measure	Motivational Interviewing n=60 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=52 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Dietary Behaviour at 1 Month Follow up	2.71 Overall score on DHQ Standard Error .04	2.67 Overall score on DHQ Standard Error .04

SECONDARY outcome

Timeframe: Mean dietary behaviour score as measured by the overall DHQ score, 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Dietary behaviour was measured by the Fat-related Dietary Habits Questionnaire (DHQ; Kristal, Shattuck, & Henry, 1990). This self-report questionnaire assesses dietary behaviours and high-fat eating patterns and consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The DHQ consists of an overall summary score and five subscale scores assessing different dimensions of fat-related dietary habits. The overall summary score is the mean of all non-missing subscales scores. Responses are scored on a 4-point scale (usually, often, sometimes, rarely/never). Range of overall summary score is 1 - 4. Higher scores correspond to higher fat intakes (i.e., higher scores = worse outcome).

Outcome measures

Measure	Motivational Interviewing n=60 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=56 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Dietary Behaviour at 6 Month Follow up	2.80 Overall score on DHQ Standard Error .04	2.70 Overall score on DHQ Standard Error .04

SECONDARY outcome

Timeframe: Mean blood pressure at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

A measure of systolic and diastolic blood pressure was taken in a standardized manner according to the Canadian Hypertension Education Program Guidelines (Hemmelgarn et al., 2006). Three different readings of blood pressure were taken at each time point (baseline and end of behavioural weight loss program), and the average of the three readings was taken as the measure of blood pressure for each time point.

Outcome measures

Measure	Motivational Interviewing n=64 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=64 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Blood Pressure at End of the Behavioural Weight Loss Program, Week 12 Systolic blood pressure	127.84 mmHg Standard Error 1.03	127.19 mmHg Standard Error 1.05
Blood Pressure at End of the Behavioural Weight Loss Program, Week 12 Diastolic blood pressure	77.48 mmHg Standard Error .68	77.89 mmHg Standard Error .68

SECONDARY outcome

Timeframe: Mean blood pressure 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

A measure of systolic and diastolic blood pressure was taken in a standardized manner according to the Canadian Hypertension Education Program Guidelines (Hemmelgarn et al., 2006). Three different readings of blood pressure were taken at each time point (baseline and 6 month follow up), and the average of the three readings was taken as the measure of blood pressure for each time point.

Outcome measures

Measure	Motivational Interviewing n=64 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=56 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Blood Pressure at 6 Month Follow up Systolic blood pressure	128.93 mmHg Standard Error 1.03	128.67 mmHg Standard Error 1.09
Blood Pressure at 6 Month Follow up Diastolic blood pressure	76.77 mmHg Standard Error .69	77.82 mmHg Standard Error .72

SECONDARY outcome

Timeframe: Mean eating disorder symptomology as measured by the global EDE-Q score, at the end of the behavioural weight loss program (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Eating disorder symptomology was measured using the Eating Disorder Examination-Questionnaire (EDE-Q; Fairburn & Beglin, 1994). This self-report questionnaire assesses the presence and degree of specific psychopathology associated with eating disorders over the previous 28 days. Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Outcome measures

Measure	Motivational Interviewing n=59 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=59 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Eating Disorder Symptomology at End of the Behavioural Weight Loss Program, Week 12	2.01 Global EDE-Q score Standard Error .08	2.07 Global EDE-Q score Standard Error .08

SECONDARY outcome

Timeframe: Mean eating disorder symptomology as measured by the global EDE-Q score, 1 month after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Eating disorder symptomology was measured using the Eating Disorder Examination-Questionnaire (EDE-Q; Fairburn & Beglin, 1994). This self-report questionnaire assesses the presence and degree of specific psychopathology associated with eating disorders over the previous 28 days. Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Outcome measures

Measure	Motivational Interviewing n=59 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=51 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Eating Disorder Symptomology at 1 Month Follow up	1.91 Global EDE-Q score Standard Error .08	2.13 Global EDE-Q score Standard Error .09

SECONDARY outcome

Timeframe: Mean eating disorder symptomology as measured by the global EDE-Q score, 6 months after the end of the behavioural weight loss program

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Eating disorder symptomology was measured using the Eating Disorder Examination-Questionnaire (EDE-Q; Fairburn & Beglin, 1994). This self-report questionnaire assesses the presence and degree of specific psychopathology associated with eating disorders over the previous 28 days. Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Outcome measures

Measure	Motivational Interviewing n=58 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=55 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Eating Disorder Symptomology at 6 Month Follow up	1.96 Global EDE-Q score Standard Error .08	1.92 Global EDE-Q score Standard Error .08

SECONDARY outcome

Timeframe: Mean self-efficacy related to eating patterns measured immediately after the first MI or attention control interview (week 1 to 2)

Self-efficacy related to eating patterns was measured by the Weight Efficacy Life-Style Questionnaire (WEL; Clark, Abrams, Niaura, Eaton, & Rossi, 1991). This self-report questionnaire yields five subscale scores, which rate self-efficacy for controlling eating in different situations/dimensions: negative emotions, availability, social pressure, physical discomfort, and positive activities. A global/total score (which ranges from 0 - 180) is obtained by summing the scores of each of the five subscales. Higher scores are indicative of greater self-efficacy (i.e., higher scores = better outcome).

Outcome measures

Measure	Motivational Interviewing n=69 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=66 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Self-efficacy Related to Eating Patterns After the First Motivational Interviewing or Attention Control Interview, Week 1 - 2	136.71 Global score on WEL Standard Deviation 23.79	130.71 Global score on WEL Standard Deviation 23.79

SECONDARY outcome

Timeframe: Mean self-efficacy for engaging in physical activity measured immediately after the first MI or attention control interview (week 1 - 2)

Self-efficacy for engaging in physical activity was measured by the Exercise Self-Efficacy questionnaire (ESE; Nigg & Riebe, 2002). Participants rate their confidence that they could exercise on a 5-point Likert scale for six barriers to exercise (e.g., bad weather, stress, availability of equipment). Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Outcome measures

Measure	Motivational Interviewing n=69 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=66 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Self-efficacy for Engaging in Physical Activity After the First Motivational Interviewing or Attention Control Interview, Week 1- 2	3.28 ESE score Standard Deviation .75	3.05 ESE score Standard Deviation .81

SECONDARY outcome

Timeframe: Mean self-efficacy related to eating patterns measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-efficacy related to eating patterns was measured by the Weight Efficacy Life-Style Questionnaire (WEL; Clark, Abrams, Niaura, Eaton, & Rossi, 1991). This self-report questionnaire yields five subscale scores, which rate self-efficacy for controlling eating in different situations/dimensions: negative emotions, availability, social pressure, physical discomfort, and positive activities. A global/total score (which ranges from 0 - 180) is obtained by summing the scores of each of the five subscales. Higher scores are indicative of greater self-efficacy (i.e., higher scores = better outcome).

Outcome measures

Measure	Motivational Interviewing n=67 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=62 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Self-efficacy Related to Eating Patterns After the Second Motivational Interviewing or Attention Control Interview, Week 12	148.46 Global score on WEL Standard Deviation 20.98	147.44 Global score on WEL Standard Deviation 20.75

SECONDARY outcome

Timeframe: Mean self-efficacy for engaging in physical activity measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-efficacy for engaging in physical activity was measured by the Exercise Self-Efficacy questionnaire (ESE; Nigg & Riebe, 2002). Participants rate their confidence that they could exercise on a 5-point Likert scale for six barriers to exercise (e.g., bad weather, stress, availability of equipment). Consists of a global score as well as four subscales: Eating Concern, Restraint, Shape Concern, and Weight Concern. The global score is obtained by summing the subscale scores and then dividing this sum by the number of subscales (i.e. four). Range is 0 - 6. Higher scores are indicative of greater eating disorder symptomatology (i.e., worse outcome).

Outcome measures

Measure	Motivational Interviewing n=67 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=62 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Self-efficacy for Engaging in Physical Activity After the Second Motivational Interviewing or Attention Control Interview, Week 12	3.58 ESE score Standard Deviation .65	3.49 ESE score Standard Deviation .83

SECONDARY outcome

Timeframe: Importance of change ratings measured immediately after the first MI or attention control interview (week 1- 2)

Self-report ratings of "importance of change" after the first motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how important it is for them personally to lose weight on a scale from 0 "not important" to 10 was "very important". Thus lower scores reflect lower levels of importance for change, and higher scores reflect higher levels of importance for change. Their raw score from 0 to 10 on this measure was taken as their "Importance for Change" rating score.

Outcome measures

Measure	Motivational Interviewing n=69 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=66 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Importance of Change Ratings After the First Motivational Interview or Attention Control Interview, Week 1 - 2	8.67 scores on a scale Standard Deviation 1.30	8.73 scores on a scale Standard Deviation 1.60

SECONDARY outcome

Timeframe: Readiness for change ratings measured immediately after the first MI or attention control interview (week 1- 2)

Self-report ratings of "readiness for change" after the first motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how ready they are to lose weight on a scale from 0 "not ready" to 10 was "very ready". Thus lower scores reflect lower levels of readiness for change, and higher scores reflect higher levels of readiness for change. Their raw score from 0 to 10 on this measure was taken as their "Readiness for Change" rating score.

Outcome measures

Measure	Motivational Interviewing n=69 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=66 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Readiness for Change Ratings After the First Motivational Interview or Attention Control Interview, Week 1 -2	8.64 scores on a scale Standard Deviation 1.32	8.65 scores on a scale Standard Deviation 1.22

SECONDARY outcome

Timeframe: Confidence for change ratings measured immediately after the first MI or attention control interview (week 1- 2)

Self-report ratings of "confidence for change" after the first motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how confident they feel about succeeding with losing weight on a scale from 0 "not confident" to 10 was "very confident". Thus lower scores reflect lower levels of confidence for change, and higher scores reflect higher levels of confidence for change. Their raw score from 0 to 10 on this measure was taken as their "Confidence for Change" rating score.

Outcome measures

Measure	Motivational Interviewing n=69 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=66 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Confidence for Change Ratings After the First Motivational Interview or Attention Control Interview, Week 1- 2	7.85 scores on a scale Standard Deviation 1.54	8.06 scores on a scale Standard Deviation 1.38

SECONDARY outcome

Timeframe: Importance of change ratings measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-report ratings of "importance of change" after the second motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how important it is for them personally to lose weight on a scale from 0 "not important" to 10 was "very important". Thus lower scores reflect lower levels of importance for change, and higher scores reflect higher levels of importance for change. Their raw score from 0 to 10 on this measure was taken as their "Importance for Change" rating score.

Outcome measures

Measure	Motivational Interviewing n=67 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=62 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Importance for Change Ratings After the Second Motivational Interview or Attention Control Interview, Week 12	8.52 scores on a scale Standard Deviation 1.23	8.88 scores on a scale Standard Deviation 1.54

SECONDARY outcome

Timeframe: Readiness for change ratings measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-report ratings of "readiness for change" after the second motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how ready they are to lose weight on a scale from 0 "not ready" to 10 was "very ready". Thus lower scores reflect lower levels of readiness for change, and higher scores reflect higher levels of readiness for change. Their raw score from 0 to 10 on this measure was taken as their "Readiness for Change" rating score.

Outcome measures

Measure	Motivational Interviewing n=67 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=62 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Readiness for Change Ratings After the Second Motivational Interviewing or Attention Control Interview, Week 12	8.70 scores on a scale Standard Deviation 1.14	8.86 scores on a scale Standard Deviation 1.33

SECONDARY outcome

Timeframe: Confidence for change ratings measured immediately after the second MI or attention control interview (week 12)

Population: The participant numbers above represent the number of people that were analyzed on this specific outcome measure, which varies outcome to outcome, and does not necessarily match the number of participants that completed interviews at various stages as listed in the Participant Flow Module.

Self-report ratings of "confidence for change" after the second motivational interview or attention control interview, on 11-point visual analogue scales (Miller & Rollnick, 2002). For the visual analogue scales, participants were asked to rate how confident they feel about succeeding with losing weight on a scale from 0 "not confident" to 10 was "very confident". Thus lower scores reflect lower levels of confidence for change, and higher scores reflect higher levels of confidence for change. Their raw score from 0 to 10 on this measure was taken as their "Confidence for Change" rating score.

Outcome measures

Measure	Motivational Interviewing n=67 Participants Two 45-60 minute motivational interviewing sessions focusing on ambivalence towards change. Motivational Interviewing: The semi-structured MI protocol was a 45-minute intervention based on general MI principles and guidelines, MI strategies specific to health care practice, and MI principles for obesity treatment. The MI protocol included the following components: (1) eliciting concerns about weight; (2) exploring ambivalence; (3) assessing importance and confidence for change; (4) writing a decisional balance; (5) bolstering self-efficacy; (6) looking towards the future; and (8) eliciting ideas for possible changes participant could make to work towards weight loss. Although there was slight variation, the protocol for both MI sessions consisted of similar components.	Attention Control n=62 Participants Two 45-60 minute semi-structured interviews ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits, acting as a pseudo-intervention. Attention Control: The attention control interview was a semi-structured interview ascertaining information relevant to health history, weight history, diet history, dietary and physical activity habits. The majority of questions for the control interviews were drawn from the Behavioural Weight Loss Program intake application. It was designed to be structurally equivalent to the MI session in terms of length of session, timing of sessions, and treatment modality. The goal of the attention-control interview was to provide a pseudo-intervention that controlled for factors common to attending treatment (e.g., attending treatment sessions, having personal contact with a therapist, discussing weight-related issues).
Confidence for Change Ratings After the Second Motivational Interviewing or Attention Control Interview, Week 12	8.25 scores on a scale Standard Deviation 1.20	8.39 scores on a scale Standard Deviation 1.26

Adverse Events

Motivational Interviewing

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Attention Control

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Dr. Kristin von Ranson

University of Calgary

Phone: 403.220.7085

Email: kvonrans@ucalgary.ca

Results disclosure agreements

• Principal investigator is a sponsor employee
• Publication restrictions are in place