An observational study in Athlete Assessment and Body Composition, sponsored by Atlantica - Instituto Universitario. Active, not recruiting at 1 site in Portugal. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-16.
Sponsored by Atlantica - Instituto Universitario · Observational
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.
This is a cross-sectional, quantitative observational study conducted at the Bettery® LifeLab, Atlântica - Instituto Universitário (Barcarena, Portugal). The study aims to evaluate bodybuilders of both sexes aged 18 years or older with at least 1 year of consistent resistance training experience and current self-reported use of anabolic-androgenic steroids and/or fat-burning pharmacological agents for at least 6 consecutive months.
Participants complete an online screening and demographic questionnaire assessing training history, competition background, and detailed substance use patterns, including compounds, dosages, administration routes, and duration.
Eligible participants attend a single laboratory testing session lasting approximately 90 minutes under strictly standardized morning conditions:
Fasting for at least 8 to 10 hours; Abstention from moderate-to-vigorous physical activity, alcohol, and caffeine for at least 24 hours prior to evaluation; Maintenance of normal hydration and avoidance of acute diuretic use.
Data collection procedures include:
Resting Metabolic Rate (RMR): Measured via indirect calorimetry using an open-circuit ventilated canopy system (Quark, Cosmed, Italy) in a quiet, thermoneutral room after supine rest. Gas exchange is monitored, and RMR is determined from steady-state respiratory gas parameters.
Body Composition: Evaluated using whole-body Dual-energy X-ray Absorptiometry (DXA; Hologic, USA) to quantify fat-free mass, fat mass, and bone mineral content.
Bioelectrical Impedance Analysis (BIA): Assessed using a phase-sensitive analyzer (BIA-101, RJL/Akern Systems) to quantify body water compartments, such as total body water, intracellular water, and extracellular water.
Anthropometry: Body weight, height, circumferences, and skinfold thickness measured according to International Society for the Advancement of Kinanthropometry (ISAK) standards.
Statistical Analysis:
Multiple linear regression modeling will be conducted to develop a new predictive RMR equation using body composition parameters (notably DXA-derived fat-free mass), anthropometrics, and pharmacological variables as predictors. Internal model stability and generalizability will be evaluated using leave-one-out cross-validation (LOOCV). Agreement between measured RMR and values derived from both the newly developed equation and existing standard predictive formulas will be examined using paired statistical tests and Bland-Altman plots.
Atlantica - Instituto Universitario is the lead sponsor of 2 studies on the registry; none are open to participants now.
Counted across the registry records on this site, refreshed daily.
Adult competitive or non-competitive bodybuilding and resistance-trained athletes of both sexes, aged 18 years or older, who have engaged in structured resistance training for at least 1 year (with a minimum of 3 training sessions per week) aimed at muscle hypertrophy and body composition optimization. All participants report active and ongoing use of anabolic-androgenic steroids (AAS) and/or fat-burning pharmacological agents for at least 6 consecutive months prior to study enrollment. Participants are recruited via sports clubs, gym facilities, bodybuilding networks, coaches, and digital community platforms.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Observational study with no administered clinical intervention. The study involves a one-time laboratory evaluation assessing resting metabolic rate through indirect calorimetry, body composition via DXA and BIA, anthropometry, and self-reported background regarding training and current use of anabolic and fat-burning pharmacological agents.
Resting Metabolic Rate
Measured via indirect calorimetry using an open-circuit ventilated canopy system (Quark, Cosmed, Italy). Assessment is performed in a quiet, thermoneutral room after supine rest, following an overnight fast of 8-10 hours and at least 24 hours of abstention from exercise, caffeine, and alcohol. The average RMR will be calculated from the 5-minute steady-state period showing the lowest coefficient of variation.
Time frame: Baseline
Fat-Free Mass (FFM)
Assessment of whole-body fat-free mass (kg) using a whole-body DXA scanner (Hologic, USA) following standardized positioning protocols.
Time frame: Baseline
Fat Mass (FM)
Assessment of whole-body fat mass (kg) using a whole-body DXA scanner (Hologic, USA) following standardized positioning protocols.
Time frame: Baseline
Total Body Water
Assessment of total body water (liters), intracellular water (liters), and extracellular water (liters) using a phase-sensitive bioimpedance device (BIA-101, RJL/Akern Systems).
Time frame: Baseline
Sum of 7 Skinfolds
Measurement of subcutaneous fat thickness (sum of 7 skinfolds in millimeters using a Harpenden caliper) assessed by a certified anthropometrist according to International Society for the Advancement of Kinanthropometry (ISAK) guidelines.
Time frame: Baseline
Body Circumferences
Measurement and body circumferences (waist, hip, arm, thigh, calf in centimeters) assessed by a certified anthropometrist according to International Society for the Advancement of Kinanthropometry (ISAK) guidelines.
Time frame: Baseline
Anabolic and Fat Burning Pharmacological Agents usage
Characterization of pharmacological substance exposure assessed via a structured confidential questionnaire. Parameters evaluated include classes and types of compounds used in the preceding 6 months (e.g., anabolic-androgenic steroids, clenbuterol, growth hormone, thyroid hormones), cumulative duration of use (months/years), administration routes, self-reported dosages, and current phase/cycle status (blast, cruise/TRT, cutting, or off) to analyze their association with resting metabolic rate.
Time frame: Baseline
Plan to share: No
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is active, not recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Atlantica - Instituto Universitario