Post-workout protein builds muscle, night-time protein builds strength

Protein supplements are among the most widely used products in fitness, yet precise advice on when to take them and which kind to choose has lagged behind their popularity. The idea of a window of opportunity around training has been debated for years, with some arguing timing matters greatly and others insisting only the total counts. Most individual trials test one protein against a placebo, which cannot settle the question of which timing or type is best. A network analysis that ranks many strategies against each other is one way to bring order to that debate.

The researchers searched PubMed, Web of Science, the Cochrane Library and SPORTDiscus up to May 1, 2023 for randomised controlled trials that combined protein supplementation with resistance training. They included 116 eligible trials covering 4,711 participants, which between them reported on 11 different timings and 14 different types of protein. A network meta-analysis then compared all of these against placebo and against each other. Outcomes covered muscle mass, strength measures such as handgrip and leg press, and physical performance tests.

Compared with placebo, protein taken after exercise produced the largest gains in muscle mass, adding 0.54 kg of fat-free mass and 0.34 kg of skeletal muscle. Protein taken at night was most effective for strength, adding 2.85 kg to handgrip and 12.12 kg to leg press strength, all rated moderate certainty. Milk proteins, including whey, casein, yogurt and milk itself, along with red meat and mixed protein, were effective for both muscle mass and strength. Notably, no timing or type of protein significantly improved physical performance on the timed up-and-go test, the 6-minute walk or gait speed.

This complicates the popular framing of a single anabolic window: the best timing appears to depend on the goal, with post-exercise intake favouring mass and night-time intake favouring strength. It also reinforces the standing of milk-based proteins, which have long been the most studied supplement type. Because almost none of the underlying trials compared timings or types head-to-head, the rankings rest on indirect evidence, and the authors call for direct comparison trials. The complete absence of effects on functional performance tests is a reminder that gains on a leg press do not automatically translate into everyday movement.

If you lift weights and use a protein supplement, this is a reason to think the clock may matter modestly, and differently depending on whether your priority is size or strength. It also supports the view that ordinary milk-derived proteins hold their own against more exotic options. The effects, while real, are measured in fractions of a kilogram of lean mass over whole trials, so timing is a refinement rather than a transformation.