Protein Plus Lifting Added 7.4 kg to the Squat, 2.6 kg to Bench

Jeff's Daily Pick. Lifting weights builds strength. Adding a protein supplement on top added another 7.4 kg to young adults' squat, across 23 trials.

In China, researchers published a meta analysis in Frontiers in Nutrition in October 2026 asking whether protein supplements add strength beyond what resistance training alone delivers in healthy young adults. They searched PubMed, Web of Science, the Cochrane Library and SPORTDiscus through April 1, 2026, and pooled 23 randomized controlled trials with 611 participants.

The pooled result

Compared with resistance training alone, training plus protein supplementation improved bench press strength by a weighted mean difference of 2.63 kg (95% CI 0.77 to 4.49; p = 0.006) and squat strength by 7.40 kg (95% CI 2.15 to 12.66; p = 0.006). The squat confidence interval is wide, from about 2 to almost 13 kg, which reflects differences between the trials.

When it worked

Subgroup analysis showed the extra squat strength mainly when the intervention lasted 12 weeks or less, or when protein was taken both around exercise and before sleep. Meta regression identified duration as a significant moderator (p = 0.037) and timing as borderline. A shorter program showing the larger gain is unexpected and may reflect which trials happened to be short rather than a real time effect.

How it compares

The best known earlier analysis, by Morton and colleagues in the British Journal of Sports Medicine in 2018, pooled 49 studies with 1,863 participants and found protein added 2.49 kg to one repetition maximum strength and 0.30 kg of fat free mass, with gains plateauing around 1.6 g of protein per kg of body weight per day. A 2026 Bayesian network meta analysis of 36 trials ranked whey first for lean mass. The new result is consistent: protein helps at the margin when people train, and the training does most of the work. Our piece on building muscle without meat covers the protein source question.