Impact of Diet-induced Change in Energy Balance on Metabolism in Endurance Athletes

NCT ID: NCT07122778

Last Updated: 2025-08-14

Basic Information

• Recruitment Status: NOT_YET_RECRUITING
• Clinical Phase: NA
• Total Enrollment: 20 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-08-31
• Study Completion Date: 2027-05-31

Brief Summary

Recent research has suggested that increasing levels of physical activity are associated with a reduction in the independent components that contribute to total energy expenditure (such as resting metabolic rate and non-exercise movement) - this occurs to conserve energy required for physical activity where energy provision becomes scarce. There are potential deleterious health and performance consequences of a reduced energy supply to fundamental metabolic processes, putting individuals regularly undertaking high levels of physical activity, such as endurance athletes, at risk. However, this association is largely based on observational data in only moderately active populations, and it is currently unclear what role energy balance status and biological sex has on this relationship.

This research intends to address these unknowns by assessing the impact of diet-induced manipulation of energy balance (conditions of energy deficit and energy surplus) in individuals undertaking habitually high levels of physical activity on independent components of total energy expenditure (resting metabolism, exercise and non-exercise movement).

Male and female athletes conducting regular moderate-to-high training volumes will undertake a randomised crossover study with a 7-day state of energy deficit and a 7-day state of energy surplus. Participants will continue to live and train as normal, but their diet will be controlled by specific food provision over the intervention periods in order to facilitate both conditions. Independent components of energy expenditure, markers of health, metabolism and performance will be measured to allow for comparison of conditions.

Detailed Description

People with very active lifestyles such as athletes, dancers, and military personnel, need to eat a lot of food to make up for the large amount of energy they burn. If they don't match their food intake to their energy needs, they may enter a state of 'energy deficit'. This means their bodies are burning more calories than they're taking in, which can lower performance, increase the risk of injuries and illnesses, and potentially harm overall health.

Traditional scientific understanding assumes that more doing physically activity leads to burning more calories (the 'additive' model). However, newer studies suggest that the body might have built-in safeguards to limit how many total calories it burns, no matter how much a person exercises. This idea (the 'constrained' model) proposes that when people exercise more, their bodies might compensate by slowing down other metabolic processes to keep overall energy use within a certain range. Although this mechanism could help the body conserve energy, it may also mean that essential functions (like immune system support and reproductive function) can become impaired.

Most research on energy deficit so far has focused on people with normal or moderate levels of physical activity. Because extremely active people experience far higher daily energy demands, the 'constrained' mechanisms could manifest differently or to a greater degree and the negative health and performance consequences might be more severe. There is also limited knowledge about how quickly these changes in energy use begin and how they affect important processes at the cellular level, such as muscle mitochondrial function or immune cell health.

This study aims to fill these gaps by measuring total energy use (and its separate parts) in highly active individuals under two conditions: when participants eat enough to cover their energy demands and when participants are purposely in an energy deficit (intentionally eating less than they need). One of our main goals is to measure changes in resting metabolic rate (RMR), which is the energy the body uses at rest to keep vital functions going. Investigators will also examine cellular changes by looking at indicators like immune cell function to see how these might help us detect early signs of harmful energy shortages.

By understanding whether, and to what extent, the body's energy use is 'constrained', investigators can develop better guidelines to help very active individuals avoid unhealthy energy deficits. Ultimately, this research could improve both performance and long-term health for athletes, military personnel, dancers, and anyone else who regularly exercises at high levels.

Conditions

Energy Balance; Energy Deficit; Low Energy Availability; Relative Energy Deficiency in Sport

Study Design

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

Study Groups

Energy deficit

Diet-induced 50% energy deficit (based on estimated average total daily energy expenditure) by allocation of pre-made meals and snacks over 7-days

Group Type: EXPERIMENTAL

Controlled energy-deficit diet

Intervention Type: DIETARY_SUPPLEMENT

Participants receive a prepared diet providing approximately 50% of their estimated daily energy expenditure to induce a sustained energy deficit

Energy surplus

Diet-induced energy surplus (approximately 500-1000kcal/day) achieved by allocation of additional snacks to be consumed on top of habitual free-living diet, to avoid inadvertent energy deficit

Group Type: EXPERIMENTAL

Habitual diet with surplus snacks

Intervention Type: DIETARY_SUPPLEMENT

Participants continue their normal diet with the addition of high-calorie snack items to achieve an approximate daily energy surplus

Interventions

Controlled energy-deficit diet

Participants receive a prepared diet providing approximately 50% of their estimated daily energy expenditure to induce a sustained energy deficit

Intervention Type: DIETARY_SUPPLEMENT

Habitual diet with surplus snacks

Participants continue their normal diet with the addition of high-calorie snack items to achieve an approximate daily energy surplus

Intervention Type: DIETARY_SUPPLEMENT

Other Intervention Names

Energy deficit; Energy surplus

Eligibility Criteria

Inclusion Criteria

• Self-identified endurance-trained sport participants
• Training volume: >7 hours per week endurance training
• Training frequency: at least 5 days per week

Exclusion Criteria

• Diagnosis of Relative Energy Deficiency in Sport (REDs)
• Active eating disorder (EDE-Q)
• Active flare of a chronic disease (e.g. inflammatory bowel disease)
• Type 1 or 2 diabetes mellitus
• Untreated or undergoing active treatment of anaemia (any cause)
• Current injury which precludes undertaking high volume endurance training
• Individuals following a habitual low-carbohydrate, high-fat diet
• Any medical diagnosis which precludes intense exercise (e.g. untreated cardiac arrhythmia)
• Allergy or intolerance to study foods
• Blood donation within preceding 8 weeks of study start date
• Use of medications that affect substrate utilisation (e.g. statins, corticosteroids, thyroxine, HRT)
• For females: current pregnancy, breastfeeding within past 6 months or post-menopausal
• Unable to undertake a treadmill running test
• Participation in any research study in the past 8 weeks
• Participation in a research study within the past year involving more than one DEXA scan
• Unable to provide informed consent due to impaired cognitive capacity or decision-making ability

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 49 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Royal Centre for Defence Medicine

OTHER_GOV

Sponsor Role: collaborator

University of Bath

OTHER

Sponsor Role: lead

Responsible Party

Josh Bakker-Dyos

Principal Investigator

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

University of Bath

Bath, , United Kingdom

Countries

United Kingdom

Central Contacts

Joshua J Bakker-Dyos, BSc(Hons) MBChB

Role: CONTACT

jbd28@bath.ac.uk

+447740191473

Facility Contacts

Joshua J Bakker-Dyos

Role: primary

jbd28@bath.ac.uk

+447740191473

Other Identifiers

345572

Identifier Type: OTHER

Identifier Source: secondary_id

6854-11590

Identifier Type: -

Identifier Source: org_study_id