How much protein do you actually need to build muscle?

If you’ve spent any time in a gym or scrolling fitness Instagram, you’ve may have heard the number: 1.6 grams of protein per kilogram of bodyweight per day. It gets repeated like gospel — and it does come from real science. A 2018 meta-analysis pooling 49 studies and nearly 1,900 people found a “breakpoint” around 1.6 g/kg, beyond which extra protein stopped adding much to muscle and strength gains.
But here’s the part that never makes it into the infographic: that breakpoint wasn’t statistically significant (p=0.079), and its confidence interval ran from roughly 1.0 to 2.2 g/kg. The data couldn’t actually pin down where the ceiling was — it just handed us a tidy, round number.
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The dose–response curve isn’t a cliff-edgeThe relationship between protein intake and muscle gain looks less like a hard stop and more like a long, gentle taper.

Newer research pushes the ceiling higher. A 2021 meta-analysis modelled intake against muscle gain using spline regression — letting the data curve rather than forcing a straight line — and found benefits continuing up to roughly 2–3 g/kg, with steadily diminishing returns. A 2022 meta-analysis in the Journal of Cachexia, Sarcopenia and Muscle went further, finding resistance-trained people eating 1.6 g/kg or more kept gaining more lean mass than those below it, with no clean plateau even past 2.2 g/kg.
None of this means “more is always better.” But the “1.6 g/kg and stop” framing is probably too tidy for anyone training seriously.

The “30 g per meal” myth doesn’t hold up
The other rule I hear constantly: your body “can only use” about 25–30 g of protein per meal, so anything beyond that is wasted.
A 2023 Maastricht University study tested this directly, having people eat 0 g, 25 g, or 100 g of protein after a resistance workout, then tracking amino acids with isotope tracers for 12 hours. The 100 g dose wasn’t wasted — it kept muscle protein synthesis elevated across the full 12-hour window, and roughly 13% of it was incorporated into muscle tissue, far more total uptake than the 25 g dose produced. Digestion just takes longer at higher doses. It doesn’t switch off.

The catch: protein isn’t magic
Before you double your protein shakes, a genuinely important caveat. A 2026 commentary in The Journal of Physiology, responding to the newest US dietary guidance, made a point I think gets lost here: simply increasing protein intake without increasing physical activity is unlikely to do much for muscle health at all.
Protein gives your muscles raw material to grow, but the growth signal comes from training.

More protein on the sofa does very little; more protein alongside progressive resistance training is where these numbers actually apply.

What I’d actually do about it

• If you’re training seriously for muscle or strength, aim for roughly 1.6–2.2 g of protein per kg of bodyweight per day — treat 1.6 g/kg as a sensible floor, not a hard ceiling.
• Don’t stress about hitting an exact per-meal number. 3–4 protein-containing meals spread reasonably evenly across the day works fine for almost everyone.
• Prioritise the training stimulus first. Protein amplifies a training effect that has to already exist — no amount of protein timing fixes a program that isn’t progressively overloading.
• If you’re not sure where you land, track your intake for 3–4 typical days before changing anything. Most people are closer to their target than they think.

References

1. Morton RW, Murphy KT, McKellar SR, et al. 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. 2018;52(6):376-384.
2. Tagawa R, Watanabe D, Ito K, et al. Dose-response relationship between protein intake and muscle mass increase: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. 2021;79(1):66-75.
3. Nunes EA, Colenso-Semple L, McKellar SR, et al. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. Journal of Cachexia, Sarcopenia and Muscle. 2022;13(2):795-810.
4. Trommelen J, van Lieshout GAA, Nyakayiru J, et al. The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans. Cell Reports Medicine. 2023;4(12):101324.
5. Højfeldt K, et al. Increasing protein intake without increased physical activity is unlikely to improve muscle health: the new U.S. dietary guidelines. The Journal of Physiology. 2026.