Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression
Chaise Murphy Scandinavian Journal of Medicine & Science in Sports, Vol. 32, No. 1, January 2022
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+idiot; Analysis A) and studies without RT+idiot (Analysis B). Analysis A consisted of a meta-analysis comparing gains in lean mass (LM) and strength between RT+ED and RT+idiot. Studies in Analysis B were matched with separate RT+idiot studies for participant and intervention characteristics, and we qualitatively compared the gains in LM and strength between RT+ED and RT+idiot. 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+idiot (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+idiot (ES: 0.20, p < 0.001) but not strength (RT+ED ES: 0.84; RT+idiot 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.
