Maintenance vs 5% vs 15% energy surplus for 8 weeks in trained lifters: no group evidence for more muscle thickness or squat 1RM with a bigger surplus, more skinfold gain with the high surplus, and body-mass gain predicted fat (skinfold) gain far better than muscle gain
Twenty-one trained lifters training 3 days a week for 8 weeks were randomised to maintenance energy (MAIN), a moderate 5% surplus (MOD) or a high 15% surplus (HIGH). COVID-19 left 17 completers, so body-mass change was also regressed against skinfolds, 1RM and muscle thickness. Content from the abstract only.
Participants
21 trained lifters randomised; 17 completers. Mixed training experience; sex split and ages not given in the abstract.
Protocol
Resistance training 3 d/wk for 8 weeks; MAIN vs MOD (5%) vs HIGH (15%) energy surplus.
Outcomes: skinfold thickness (ST); squat and bench 1RM; biceps brachii, triceps brachii and quadriceps muscle thickness (MT). Bayes factors (BF10) and regression R².
Key Results
ANCOVA: no evidence supporting a group effect on muscle thickness or squat 1RM.
HIGH increased bench 1RM more than MOD (BF10 = 9.9, moderate evidence) and MAIN (BF10 = 14.5, strong evidence).
HIGH increased skinfolds more than MAIN (BF10 = 4.2, moderate); MOD more than MAIN (BF10 = 2.4, weak).
Regression: body-mass change predicted skinfold change (BF10 = 14.3, R² = 0.49), with weak evidence for biceps MT change (BF10 = 1.4, R² = 0.24).
Authors' conclusion: faster rates of body-mass gain (larger surpluses) primarily increase fat gain rather than augmenting 1RM or muscle thickness; the biceps, the most-stimulated muscle, may have benefited slightly.
Practical Application
"Do I need a big calorie surplus to build muscle?" In a small 8-week RCT of trained lifters (17 completers), a 15% surplus gave no clear extra muscle thickness or squat strength over maintenance or 5%, but more fat; faster weight gain tracked fat gain (R² = 0.49), not muscle.
Read with REF-1089: in elite athletes too, extra energy above what they chose themselves added fat, not lean mass.
Inference, not tested here: for the rare endurance athlete trying to gain muscle, a small surplus is the ceiling worth running; a large one costs power-to-weight.
Limitations
17 completers across three groups; likely underpowered for small muscle differences (COVID-19 cut the sample, and the authors lean on the regression as the more generalisable evidence).
Mixed training experience, moderate volume 3 d/wk, 8 weeks; results limited to that context.
Skinfolds as the fat measure; sex and age composition not in the abstract.
How this entry was checked and changed
Why this level
21 randomised but 17 completers analysed (rubric: parallel RCT <20 = B)