REF-1087 · Murphy & Koehler, 2022 · Scandinavian Journal of Medicine & Science in Sports, · Paper · PubMed
Resistance training in an energy deficit: lean-mass gains are impaired (ES −0.57) but strength gains are comparable (ES −0.31, p = 0.28), and a meta-regression put the deficit that prevents lean-mass gain at ~500 kcal/day
Meta-analysis of RCTs lasting ≥3 weeks
A systematic review of PubMed and SportDiscus for RCTs performing resistance training in an energy deficit (RT+ED) for ≥3 weeks. Analysis A meta-analysed studies with a parallel no-deficit control (RT+CON); Analysis B matched deficit studies with separate RT+CON studies; both were pooled into a meta-regression of lean mass on deficit size. Content from the abstract only.
Participants
RCTs with resistance training in an energy deficit for ≥3 weeks; the numbers of studies and participants are not given in the abstract.
Protocol
Analysis A: meta-analysis of lean-mass (LM) and strength gains, RT+ED vs RT+CON within the same trials.
Analysis B: RT+ED studies matched to separate RT+CON studies for participant and intervention characteristics; qualitative comparison.
Meta-regression pooling A and B: magnitude of the energy deficit vs LM change.
Key Results
Analysis A: LM gains impaired with RT+ED vs RT+CON (effect size −0.57, p = 0.02); strength gains comparable (ES −0.31, p = 0.28).
Analysis B: strength was not impaired (RT+CON ES 0.81; RT+ED ES 0.84), but LM was — RT+CON ES 0.20 (p < 0.001) against RT+ED ES −0.11 (p = 0.03).
Meta-regression: a ~500 kcal·day⁻¹ energy deficit prevented LM gains.
Authors' conclusion: those lifting to build lean mass should avoid prolonged energy deficiency; those lifting to preserve lean mass during weight loss should avoid deficits >500 kcal·day⁻¹.
Practical Application
"Can I put on muscle while I'm cutting?" A meta-analysis of RCTs lasting ≥3 weeks found that lifting in an energy deficit still built strength as well as lifting without one, but lean-mass gains were impaired (ES −0.57), and a deficit of about 500 kcal a day was enough to stop them.
So during a weight-loss phase, the realistic aim of the gym is to keep muscle and strength, not to grow; a deficit kept under ~500 kcal/day protects lean mass.
Strength rising during a cut is not evidence that muscle is growing — the two came apart here.
Limitations
Numbers of trials and participants, populations, deficit methods and body-composition methods are not given in the abstract.
Analysis B compares separate studies (matched, qualitative), which is weaker than within-trial comparison.
The ~500 kcal/day figure comes from a meta-regression across studies — a between-study association, not a tested individual threshold.
How this entry was checked and changed
Why this level
SR/MA of controlled trials; number of trials and participants not given in the abstract, and Analysis B compares matched separate studies rather than randomized arms