Resistance exercise training, combined with protein supplementation, is a common practice among athletes and recreational exercisers seeking added muscle strength and mass. Many studies had been published on this topic, but with conflicting results.
Researchers systematically reviewed the existing literature and pooled results from 49 high-quality studies which included 1,863 people – men and women, old and young, and with various exercise experience. Only randomized-controlled trials that included a resistance exercise component that lasted at least six weeks were included.
People who consumed more protein gained about 25% in muscle mass and 10% in strength compared to the control group. Researchers found 1.6 grams of protein per kilogram of body weight per day was ideal. For a 130 lb (59 kg) woman, this equates to about 94 grams of protein per day. Beyond that, more protein did not yield additional gains. Any time of day and any type of protein, e.g. solid or liquid, soy or beef, was fine.
This is the largest meta-analysis on this subject to date.
Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., … & Phillips, S. M. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med, 52(6), 376-384.
