Energy deficiency impairs resistance training gains in lean mass but not strength: A meta‐analysis and meta‐regression
Chaise Murphy, Karsten Koehler
Abstract
Short‐term energy deficits impair anabolic hormones and muscle protein synthesis. However, the effects of prolonged energy deficits on resistance training (RT) outcomes remain unexplored. Thus, we conducted a systematic review of PubMed and SportDiscus for randomized controlled trials performing RT in an energy deficit (RT+ED) for ≥3 weeks. We first divided the literature into studies with a parallel control group without an energy deficit (RT+CON; Analysis A) and studies without RT+CON (Analysis B). Analysis A consisted of a meta‐analysis comparing gains in lean mass (LM) and strength between RT+ED and RT+CON. Studies in Analysis B were matched with separate RT+CON studies for participant and intervention characteristics, and we qualitatively compared the gains in LM and strength between RT+ED and RT+CON. Finally, Analyses A and B were pooled into a meta‐regression examining the relationship between the magnitude of the energy deficit and LM. Analysis A showed LM gains were impaired in RT+ED vs RT+CON (effect size (ES) = −0.57, p = 0.02), but strength gains were comparable between conditions (ES = −0.31, p = 0.28). Analysis B supports the impairment of LM in RT+ED (ES: −0.11, p = 0.03) vs RT+CON (ES: 0.20, p < 0.001) but not strength (RT+ED ES: 0.84; RT+CON ES: 0.81). Finally, our meta‐regression demonstrated that an energy deficit of ~500 kcal · day −1 prevented gains in LM. Individuals performing RT to build LM should avoid prolonged energy deficiency, and individuals performing RT to preserve LM during weight loss should avoid energy deficits >500 kcal day −1 .