Protein and Performance (PROPER) in Endurance Athletes

NCT ID: NCT05426447

Last Updated: 2024-05-07

Basic Information

• Recruitment Status: ACTIVE_NOT_RECRUITING
• Clinical Phase: NA
• Total Enrollment: 20 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2021-02-23
• Study Completion Date: 2025-12-31

Brief Summary

The present study is a parallel group design with randomised allocation to either a 1) reduced protein diet (RP) or a 2) normal protein diet (NP). The two groups will be pair-matched based on habitual dietary protein intake, endurance training, endurance performance, and sex.

The aim of the study is to investigate the effects of reducing dietary protein (~1g protein/kg body mass) compared to an eucaloric normal protein diet (~2g protein/kg body mass) for 6 weeks in well-trained endurance athletes on endurance performance, body composition, skeletal muscle protein synthesis, and health-related outcomes.

The hypothesis is that endurance performance will maintain or even be improved in well-trained endurance athletes after a 6-week dietary intervention of an eucaloric, protein reduced diet compared to a normal protein rich diet.

Detailed Description

Design: The present study will include two phases: a 3-week run-in period, and a 6-week intervention of controlled diets containing either a reduced dietary protein (RP) or normal (habitual) protein (NP). The run-in period serves as a period for obtaining general activity data and habitual dietary and training habits in order to match the groups before entering the dietary intervention period.

Subjects and dietary goals: The study is aiming at including 20 male endurance athletes exercising ~15hrs+/week. The 20 males will be pair-matched based on habitual endurance training, habitual dietary protein intake, and endurance performance, and allocated in a randomised order to: 1) a reduced-protein diet (RP) or 2) a normal-protein diet (NP).

3-weeks run-in period: After a minimum of 7 days after written consent has been obtained, the run-in period will begin. Habitual endurance training volumes will be registered in an online platform (TrainingPeaks) and daily activity level will be monitored using an accelerometer (SENS) throughout the run-in and diet intervention period. "Heavy water" (D2O) will be ingested in a large bolus (3.5ml/kg LBM) upon beginning of the run-in period and plasma enrichments will be maintained throughout the study period by ingesting small daily boluses. This serves to determine skeletal muscle protein synthesis throughout the study.

6-weeks dietary intervention: The diets will be eucaloric and the estimated energy percentages for macronutrients will be as follows: RP - Protein ~7E%, Carbohydrate ~63E%, Fat ~29E%. NP - Protein ~16E%, Carbohydrate ~53E%, Fat ~30E%. Weekly urine and faeces samples will be collected during the run-in period and dietary intervention and the controlled diets will be supplied weekly for the participants.

Testing: Extensive endurance performance and metabolic testing will be performed prior to-, and during the intervention on weeks -1, 0 (Pre), 3 (Mid), and 6 (Post). The tests include: Body composition by DXA-scanning, resting metabolic rate by online respirometry using a Vyntus (Jaeger, PCX), venous blood-, and skeletal muscle biopsy sampling from m. Vastus Lateralis, a standardised breakfasts, endurance cycling on an electro-magnetically braked bike (Lode Excalibur) or running on a motorised treadmill (Woodway), and haemoglobin mass measuring using a modified version of the CO-rebreathing method.

The body mass will be kept unchanged during the 6-weeks dietary intervention.

Conditions

Diet, Healthy; Protein Deficiency

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

Reduced protein diet

A 6-week eucaloric dietary intervention of reduced protein intake (~1g protein/kg body mass). The diet will, hence, contain ~7E% protein, ~63E% carbohydrate, and ~29E% fat.

Participants are free-living and receive all food pre-packed from the study kitchen. The energy provision will be set to match energy balance.

Group Type: EXPERIMENTAL

Dietary intervention of reduced protein intake

Intervention Type: OTHER

6-wk dietary intervention of reduced protein intake

Normal protein diet

A 6-week eucaloric dietary intervention of normal protein intake (~2g protein/kg body mass). The diet will, hence, contain ~16E% protein, ~53E% carbohydrate, and ~30E% fat.

Participants are free-living and receive all food pre-packed from the study kitchen. The energy provision will be set to match energy balance.

Group Type: ACTIVE_COMPARATOR

Dietary intervention of normal protein intake

Intervention Type: OTHER

6-wk dietary intervention of normal protein intake

Interventions

Dietary intervention of reduced protein intake

6-wk dietary intervention of reduced protein intake

Intervention Type: OTHER

Dietary intervention of normal protein intake

6-wk dietary intervention of normal protein intake

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Endurance athlete
• Exercising at least 10hrs per week
• Habitual dietary protein intake ~2g/kg body mass
• BMI<25

Exclusion Criteria

• Food allergies that exclude the controlled diet
• Inconsistent endurance training load

• Minimum Eligible Age: 20 Years
• Maximum Eligible Age: 50 Years
• Eligible Sex: MALE
• Accepts Healthy Volunteers: Yes

Sponsors

Maastricht University Medical Center

OTHER

Sponsor Role: collaborator

University of Copenhagen

OTHER

Sponsor Role: lead

Responsible Party

Bente Kiens

Professor of Exercise, Nutrition and Metabolism, D Sci, PhD, Principal Investigator

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Nicki W Almquist, Post Doc

Role: STUDY_DIRECTOR

University of Copenhagen

Bente Kiens, Professor

Role: PRINCIPAL_INVESTIGATOR

University of Copenhagen

Locations

University of Copenhagen

Copenhagen, , Denmark

Countries

Denmark

Other Identifiers

PROPER

Identifier Type: -

Identifier Source: org_study_id