What you've heard
More protein is always better
Verdict
False
False. Past a point, extra protein stops adding muscle.
Is more protein always better?
False. Past a point, extra protein stops adding muscle.
In pooled trials, protein supplements added modestly to the strength and muscle that training builds. But the gains in lean mass stopped rising at about 1.6 grams per kilogram of body weight a day, or about three-quarters of a gram per pound. That figure is an estimate with a wide margin of error, so a few people may benefit from a little more, and the supplements helped less as age rose. Without training, extra protein made no meaningful difference to strength. Healthy kidneys handled higher-protein diets without measurable harm in mostly short trials, though four US professional societies, writing about people on weight-loss drugs, advise against staying above 2 grams per kilogram (about 0.9 grams per pound) for long, and people with serious kidney disease need their clinician's advice.21 Past the point the muscle can use, protein is just food.
Where the book tests it
What the book recommends instead
Reach the daily protein range for your age
ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.How: for a 155-pound person, the official minimum is roughly 55 grams a day and the current US goal 85 to 110 grams. Over 65, do not drop below about 70 to 85 grams, the expert-group floor; the upper part of the US range suits active older adults. In lifting trials, more than about 110 grams stopped adding muscle. (Per pound of body weight: the minimum is a little over a third of a gram, the US goal half to three-quarters of a gram, the over-65 floor about half a gram.) A protein food at each meal, such as eggs, yogurt, fish, beans, tofu or meat, is the easy way to get there (Chapter 5 covers the rest of the plate). Why: enough protein helps training build a little more muscle, and expert panels judge that older muscle needs more.
Sources
- 21.Morton, R.W., Murphy, K.T., McKellar, S.R., Schoenfeld, B.J., et al. (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." British Journal of Sports Medicine, 52(6), 376-384. https://doi.org/10.1136/bjsports-2017-097608; Tagawa, R., Watanabe, D., Ito, K., Otsuyama, T., et al. (2022). "Synergistic effect of increased total protein intake and strength training on muscle strength: a dose-response meta-analysis of randomized controlled trials." Sports Medicine - Open, 8(1), 110. https://doi.org/10.1186/s40798-022-00508-w; Devries, M.C., Sithamparapillai, A., Brimble, K.S., Banfield, L., et al. (2018). "Changes in kidney function do not differ between healthy adults consuming higher- compared with lower- or normal-protein diets: a systematic review and meta-analysis." Journal of Nutrition, 148(11), 1760-1775. https://doi.org/10.1093/jn/nxy197; Mozaffarian, D., Agarwal, M., Aggarwal, M., Alexander, L., et al. (2025). "Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society." American Journal of Clinical Nutrition, 122(1), 344-367. https://doi.org/10.1016/j.ajcnut.2025.04.023 (Morton: 49 trials; the break point is 1.62 g/kg a day, 95% CI 1.03-2.20. Devries: 28 trials on kidney function.)
Note numbers are those of Chapter 4, Load, Strength and Bone.
This verdict is one of the "What you've heard" boxes in Chapter 4, Load, Strength and Bone, where the book tests the claims people repeat against the studies behind them.
Educational content, not medical advice. Disclaimer.