Walk into any gym and ask around, and you'll hear wildly different numbers on protein — "one gram per pound of bodyweight," "as much as you can eat," or worse. Here's what the actual research supports.
The Real Research-Backed Number
A 2022 systematic review and meta-analysis in the Journal of Cachexia, Sarcopenia and Muscle, led by researchers including Stuart Phillips, analyzed protein intake data across healthy adults engaged in resistance training. The clear finding: intakes at or above 1.6 grams per kilogram of body weight per day — roughly 0.73 grams per pound — produced significantly greater gains in lean body mass in adults under 65, compared to lower intakes closer to the standard RDA of 0.8 g/kg.
For context, that's about twice the RDA, which makes sense — the RDA is calibrated to prevent deficiency in sedentary people, not to optimize muscle growth in someone lifting weights regularly.
Where the Diminishing Returns Kick In
The same review found that most of the underlying studies already had participants eating around 1.2 g/kg per day at baseline, and that pushing intake substantially higher than the ~1.6 g/kg threshold didn't keep producing proportionally bigger benefits. This matches the broader consensus in sports nutrition research: there's a real, evidence-backed target, and it's lower than a lot of gym folklore suggests. Chronically eating far beyond it isn't harmful for most healthy people, but it isn't buying you extra muscle either — the returns flatten out.
What That Looks Like in Grams
For a 180-pound (about 82 kg) man, 1.6 g/kg works out to roughly 131 grams of protein per day — a realistic, achievable target through whole food, without needing to force-feed extreme amounts.
Timing: Does It Matter?
Research on how the body uses protein per sitting suggests there's a practical ceiling on how much a single meal can contribute toward muscle protein synthesis, meaning that spreading your target across three to four meals — roughly 30–40 grams of protein each — tends to be a more effective strategy than trying to eat it all in one or two large meals.
Practical Sources
Chicken, beef, fish, eggs, Greek yogurt, cottage cheese, and a protein supplement to fill gaps are all reasonable ways to hit your number. Whole foods should do the majority of the work — supplements are a convenience tool, not a requirement.
The Takeaway
You don't need extreme protein intakes to build muscle. The best current evidence supports roughly 1.6 g/kg (about 0.73 g/lb) per day, spread across several meals, as the research-backed target for maximizing muscle growth — with diminishing returns beyond that point.
References
- Nunes, E. A., Colenso-Semple, L., McKellar, S. R., et al. (2022). Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. Journal of Cachexia, Sarcopenia and Muscle, 13(2), 795–810.
- Systematic review on how much protein the body can use in a single meal for muscle-building: implications for daily protein distribution. PMC.
Discussion