The modern natural bodybuilder: Dietary intake, supplement usage, training demands, and their health implications

Abstract

Background: Competitive bodybuilders (BB) are judged on muscularity and leanness, and follow a periodised diet and training regimen to reach competition physique. The off-season goal is to achieve a high degree of muscularity, with the in-season targeting reductions in body fat while maintaining muscle mass. This thesis aimed to investigate dietary and training strategies in addition to body composition, physiological and psychological characteristics of competitive natural BB. Methods: Following a systematic review examining muscle dysmorphia (MD) in BB and non-bodybuilder resistance trainers (NBBRT), three studies were conducted: a cross-sectional survey identifying correlates of MD; interviews with experienced BB to describe dietary strategies used during the competition cycle; an observational study examining body composition, physiological and psychological changes occurring during competition preparation and recovery. Results: The systematic review demonstrated MD symptoms are higher in BB than NBBRT (ES=0.53-1.12). Rate of weight loss (β=0.307), disordered eating symptoms (β=0.298) and bodybuilding experience (β=-0.257) correlated with MD symptoms. A high protein diet with progressive reductions in fat and carbohydrate intake, and weekly re-feed days, were used during the in-season. Participants achieved large reductions in fat mass (3.5±1.8kg; d=1.3), with a small loss of lean mass (0.6±1.4kg; d=0.1), during competition preparation. This was accompanied by reductions in testosterone (38%; d=1.6) and insulin-like growth factor 1 (26%; d=0.9), but no change in resting metabolic rate (RMR) or MD symptoms. Conclusion: A high protein intake with progressive reduction in dietary energy enabled natural BB to reduce fat mass while retaining lean mass and RMR despite reductions in anabolic hormones. MD findings suggest bodybuilding may attract those susceptible to pathological behaviours, with underlying attitudes and behaviours associated with increased symptoms.