Resting Metabolic Rate in Bodybuilders Using Performance-Enhancing Drugs

Bodybuilders present unique body composition profiles, characterized by high fat-free mass and very low levels of body fat. In addition, many competitive and non-competitive athletes use anabolic-androgenic steroids (AAS) and fat-burning pharmacological agents to enhance muscle mass and accelerate fat loss. Accurate determination of energy requirements is critical for performance and nutritional planning in this population. Resting metabolic rate (RMR) represents the largest component of daily energy expenditure. While indirect calorimetry is considered the reference method to assess RMR, it is expensive and not widely accessible, making predictive mathematical equations the primary tool used in sports and clinical settings. However, widely used equations (such as Harris-Benedict, Mifflin-St Jeor, and Cunningham) were developed in general or non-athletic populations and may systematically underestimate energy requirements in bodybuilders using performance-enhancing substances. The primary aim of this cross-sectional study is to measure resting metabolic rate via indirect calorimetry and body composition via dual-energy X-ray absorptiometry (DXA) in adult bodybuilders using anabolic and fat-burning agents. The ultimate goal is to develop and validate a population-specific predictive equation for RMR and compare its accuracy against established predictive formulas.

Inclusion Criteria: 1. Male or female individuals aged 18 years or older; 2. Current participation in bodybuilding or/and resistance training; 3. Minimum resistance training experience of at least 1 year; 4. Current self-reported use of AFBPA for at least 6 consecutive months prior to assessment; 5. Agreement to maintain usual training and dietary habits prior to assessment; 6. Ability to provide informed consent. Exclusion Criteria: 1. Present any diagnosed metabolic, cardiovascular, renal, or endocrine disease that may significantly affect RMR; 2. Present acute illness or injury at the time of assessment, affecting energy requirements. 3. Fail to comply with pre-assessment instructions, including fasting requirements or abstention from exercise, alcohol, or caffeine; 4. Present incomplete assessment data. 5. Unable to attend the assessments at the laboratory. 6. Failure to provide informed consent.