Protein powder is the most common supplement in gyms. Two meta-analyses show how much it adds when you lift, and where the benefit levels off.
The largest analysis
A 2018 meta-analysis in the British Journal of Sports Medicine pooled 49 studies with 1,863 participants. Protein supplementation during prolonged resistance training increased one-rep max strength by about 2.5 kg, fat-free mass by about 0.30 kg and muscle fibre size. The benefit was smaller with increasing age and larger in people with more training experience. Intakes above about 1.6 g per kg of body weight per day did not add further resistance-training gains.
An earlier analysis
A 2012 meta-analysis in the American Journal of Clinical Nutrition covered 22 randomised trials with 680 participants. Protein supplementation increased fat-free mass by about 0.69 kg and leg press strength by about 13.5 kg compared with placebo, in both younger and older adults.
Practical takeaways
- Protein powder helps most when your diet falls short of your daily target.
- Around 1.6 g per kg per day is where extra protein stopped adding gains in the 2018 analysis. The ISSN suggests 1.4 to 2.0 g per kg for building muscle.
- Effects are modest: a few hundred grams of lean mass over a training block, not miracles.
- Choose third-party tested products. See our whey review.
Frequently asked questions
How much protein do I need to build muscle?
The 2018 meta-analysis found no further benefit above about 1.6 g per kg per day. The ISSN suggests 1.4 to 2.0 g per kg.
Does protein powder work better for beginners or experienced lifters?
The 2018 analysis found protein supplementation was more effective in resistance-trained individuals and less effective with increasing age.
How much extra muscle does protein powder add?
Around 0.3 to 0.7 kg of fat-free mass over a training period in the two meta-analyses, so the effect is real but modest.
References
- Morton RW 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. Br J Sports Med. PubMed 28698222
- Cermak NM et al. (2012). Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis. Am J Clin Nutr. PubMed 23134885
General information, not medical advice. Check with a doctor before starting a new training or supplement routine. Last updated 27 October 2026.
