You need protein within 30 minutes of training

Trials that gave the same amount of protein either right around a workout or hours away from it have mostly found no difference in the muscle and strength people gained. Pooled analyses of randomized trials point to total protein intake, rather than timing, as the factor most associated with muscle growth. When total protein was accounted for, the apparent advantage of protein taken within an hour of training was no longer statistically significant.

The results that point the other way come from specific settings. One small 2001 trial in 13 men in their seventies found muscle growth only when 10 g of protein came immediately after training rather than two hours later. A 2025 double-blind trial in 30 older men (average age 66) used 40 g and found no difference between protein taken right after training and protein taken before bed. A 2024 network analysis ranked post-exercise protein among the more effective timings, but it compared each timing with no protein at all rather than with the same dose at another time. None of the trials cited here tested a 30-minute cutoff against a later one.

The most direct evidence comes from trials that held the protein dose equal and changed only when it was taken. A 2025 meta-analysis pooled the five randomized trials that compared the same dose before or after training for at least four weeks. Lean mass gains did not differ, and chest press strength did not differ. Leg press strength rose more when protein came before training (p = 0.048), although the difference between the upper and lower body results was not statistically significant. One of the five, a 2017 trial in 21 trained young men, found no difference between 25 g of whey taken immediately before or immediately after training. Two trials outside that analysis moved the protein hours away from the workout. A 2024 trial in trained young men, 31 of whom finished, compared 25 g of whey immediately before and after training with the same doses three hours before and three hours after, with both groups aiming for 2 g of protein per kg of body weight a day; muscle and strength gains did not differ over eight weeks. A 2020 double-blind trial in 34 postmenopausal women found no difference between 30 g of whey taken right after training or in the afternoon.

Broader pooled analyses show a similar picture. A 2013 meta-regression of 23 hypertrophy trials found a small unadjusted advantage for protein within an hour of training that did not hold once total protein intake was included, and its included trials were not required to match total protein between groups. A 2020 review of 65 trials found protein supplementation added about 0.6 kg of lean mass in adults, with no timing subgroup showing an advantage. The 2013 analysis was funded by a protein supplement company, the 2017 trial used protein donated by the same company, and the 2025 trial in older men was partly funded by it. The 2024 trial names the managing director of a pharmaceutical company as its supporter.

On the biology, eating protein after resistance exercise raises muscle protein synthesis, which is where the idea of a short window began. Tracer work has since measured that response lasting more than 12 hours after a large dose, and the NIH Office of Dietary Supplements describes the post-exercise period as lasting up to 24 hours. The one trial suggesting timing mattered, in older men, used 10 g of protein, less than the 25 to 40 g per serving used in the later head-to-head trials.