Does the timing of protein matter for muscle gain?

A 2025 meta-analysis of five randomised trials that directly compared protein taken before and after training found no difference in lean body mass gains (SMD -0.08, 95% CI -0.398 to 0.244). The review, in Nutrients, saw a possible difference in leg press strength, but the certainty of that finding was very low.

What did the 2025 meta-analysis compare?

Earlier meta-analyses did not directly compare several timings within the same study. Casuso and Goossens, Nutrients 2025 included only trials that randomised people to protein before or after each training session for at least four weeks. Of 3,311 records screened, six reports covering five studies qualified.

Participants were mixed: young trained adults, older untrained adults, and older adults with overweight or obesity and type 2 diabetes.

For lean body mass, the pooled difference was SMD -0.08 (95% CI -0.398 to 0.244), with no heterogeneity between studies. The authors concluded that protein timing does not importantly modify exercise-induced changes in lean mass. For chest press strength the difference was also negligible (SMD 0.07, 95% CI -0.248 to 0.395).

The interval spans zero on both sides, so the data are compatible with small effects in either direction. The review does not address protein spread across the day.

Does timing change strength, and how firm is this?

Leg press was the exception. The pooled difference favoured protein before training (SMD 0.70, 95% CI 0.005 to 1.388), an interval that only just excludes zero. A test comparing leg press and chest press did not show the two differ significantly (p = 0.07), and the certainty for leg press was rated very low. The authors say more investigation is needed.

Certainty was downgraded for risk of bias and imprecision (low for lean mass and chest press), some analyses rested on just two observations, and there were too few studies for meta-regression.

This agrees with an older analysis. Schoenfeld et al., 2013 pooled 20 strength and 23 hypertrophy studies and found no significant timing effect once covariates were controlled, with total protein intake the strongest predictor of hypertrophy. The question of how much is covered in what the evidence says about protein amounts.

The bottom line

• In five trials directly comparing protein before versus after training, lean body mass change did not differ (SMD -0.08, 95% CI -0.398 to 0.244).
• A possible leg press difference (SMD 0.70) rested on very low certainty and was not confirmed by a formal comparison with chest press.
• The evidence base is small, so the finding describes these trials, not every training population.