Fat-Free Mass Accretion: Limits, Targets, and Best Practices

ABSTRACT

This review examines physiological limits, longitudinal projections, and best practices for muscle hypertrophy with a focus on bodybuilding and physique sport. Recurring body composition assessments using multicompartment models are recommended for monitoring short-term fat-free mass (FFM) changes and long-term muscular development. Normative data indicate that drug-free male athletes typically gain roughly 1.4 kg of FFM over 12 weeks of resistance training, with an interquartile range of 1–2 kg. A practical upper limit for FFM index in drug-free male athletes is approximately 28.5, although higher values have been observed in the context of elevated adiposity or anabolic androgenic steroid use. Female athletes tend to have roughly 70% less FFM at baseline but make proportionally similar FFM gains in response to resistance training. The present review models plausible short-term and long-term growth trajectories for both male and female lifters. Training practices that optimize hypertrophy include moderate loads (6–12 repetition maximum), training near muscular failure, and sufficient weekly volume (12–30 fractional sets per muscle group). Nutritional factors include maintaining modest caloric surpluses (0.1–0.25% body weight gain weekly), adequate protein intake (1.6–2.2 g/kg/d), sufficient carbohydrate intake (≥3 g/kg/d), and moderate fat intake (0.5–1.5 g/kg/d). Creatine and protein supplementation provide established hypertrophic benefits, while evidence for other supplements remains inconclusive.