How much protein to build muscle?
You've heard “a gram per pound.” That's a rule of thumb someone rounded off decades ago.
Here's what 49 studies actually found — and what it means for your weight.
No email. No account. The number is yours either way.
Your number
160 g a day
That's 1.9 g for every kilo you weigh.
Inside the 1.4–2.0 g/kg sports-nutrition bodies recommend for lifters
Most days it's the same six. See sixteen other people's days →
Where that number comes from
Every serious answer to this question lands in the same narrow band: 1.6 to 2.2 grams per kilo of bodyweight. Below it you leave results on the table. Above it, the research stops finding a difference.
For lifting, that ceiling has a number on it. Morton's team pooled 49 studies and found gains in lean mass plateau at about 1.62 g/kg a day — more protein past that point didn't build more muscle. The confidence interval reaches 2.2, which is where the familiar range comes from.
For losing weight, the band shifts up rather than down. A deficit is catabolic, so protein needs go up exactly when appetite goes down. Clinical guidance for people on a GLP-1 starts at 1.2 g/kg and moves to 1.6–2.0 for anyone strength training.
Same number. Opposite direction.
Eat in a surplus and protein decides whether the extra becomes muscle or fat. Eat in a deficit and protein decides whether the loss comes off as fat or as muscle.
Same mechanism, pointed two ways — and the deficit side needs slightly more, which is the part that surprises people. Cutting food usually means cutting protein too, and that's exactly backwards.
| What you're doing | Grams per kilo | Where it comes from |
|---|---|---|
| Keep what I have | 1.6 | Where the benefit plateaued across 49 studies (Morton, 2018) |
| Build muscle | 1.9 | Inside the 1.4–2.0 g/kg sports-nutrition bodies recommend for lifters |
| Lose fat, keep muscle | 2.2 | A deficit needs more — 2.3–3.1 g/kg of lean mass (Helms, 2014) |
| Losing on a GLP-1 | 2.2 | Protein plus lifting protected lean mass in trials (2025) |
Losing fat and losing on a GLP-1 are the same number, because they're the same problem. The drug changes how hard it is to eat that much — not how much you need.
About lean mass
Some of what comes off during weight loss is lean tissue. That's true of any weight loss, and it's true on a GLP-1 — trials have put it at roughly a quarter to 40% of the total. In SURMOUNT-1, about 75% of the weight lost was fat and 25% was lean.
The picture is genuinely mixed, and anyone telling you otherwise is selling something. A semaglutide study found lean mass preserved, grip strength improved, and the share of participants with sarcopenic obesity falling from 49% to 33%.
What's consistent across all of it is which lever moves: protein, plus resistance training. In a 2025 case series of patients on semaglutide and tirzepatide eating 1.6–2.3 g per kilo of fat-free mass and lifting three to five times a week, one lost a third of his bodyweight with under 9% of it lean — and two of the three gained lean tissue while losing weight.
People who hit their protein kept it. Some gained.
You don't control the drug's effect on your appetite. You control the protein. That's the part this page is about.
Morton et al., Br J Sports Med, 2018 · Look et al., Diabetes Obes Metab, 2025 (SURMOUNT-1 body composition) · SEMALEAN, 2025 · Lean soft tissue case series, 2025 · Helms et al., 2014
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