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

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.

Conditions

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

Interventions

DIETARY_SUPPLEMENT

Controlled energy-deficit diet

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

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

Sponsors & Collaborators

• Royal Centre for Defence Medicine

  collaborator OTHER_GOV

• University of Bath

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

NONE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

49 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-08-31

Primary Completion

2026-08-31

Completion

2027-05-31

Countries

• United Kingdom

Study Locations