What a small four-week trial and a big meta-analysis say about daily protein for lifters, and how to hit your number.
Eating more protein helped a group of lifters add muscle in just four weeks. The catch is that the trial was small, and the bigger picture is more modest than the headlines.
What the four-week trial tested
In a 2025 randomized trial in Scientific Reports, 34 sedentary young men did resistance training for four weeks. Both groups ate the same standardized meals. One group got whey protein to reach 1.5 g per kg of bodyweight a day (about 0.7 g per lb). The other stayed at 0.8 g/kg.
Only the protein group gained significant muscle mass and strength. Their resting metabolic rate (the calories you burn at rest) also rose.
Key things to know
- Training comes first. In a meta-analysis of 49 trials, lifting alone was the stronger driver, and protein added about 0.3 kg of lean mass on top.
- Gains level off. In that same analysis, extra protein stopped adding lean mass beyond roughly 1.6 g/kg a day.
- Sports nutrition guidance agrees. The ISSN position stand recommends 1.4–2.0 g/kg a day for building and keeping muscle.
- Age matters. The benefit of added protein shrank with each year of age, and trained lifters got more out of it than beginners, per the same meta-analysis.
What the trial did not show
Some claims you’ll see online go further than the data. Fat oxidation rose in both groups, and both lost body fat, so that isn’t a protein effect. Liver fat dropped in both too, though the protein group had a bigger improvement in liver enzymes.
The trial was short, small and men-only, and it used a body-composition scale rather than a scan. That makes it one useful data point and nothing more.
Key takeaway: Around 1.5–1.6 g/kg a day is a well-supported target for lifters. Going far past it hasn’t been shown to build more muscle.
Spreading it out
The ISSN suggests about 0.25 g/kg per meal, or 20–40 g, every 3–4 hours. For more on this, see our piece on protein needs after 40 and per-meal dosing.
Putting it into practice
For an 80 kg lifter, 1.6 g/kg is about 128 g a day, or roughly four meals of 30–35 g. The math is easy. Doing it every day is the hard part.
That’s where Proteinly fits. It’s a protein-first app with no calorie counting, and its automatic eating timer reminds you to eat every 2 hours, so regular protein becomes a habit. It helps with consistency and makes no promises about muscle.
Frequently asked questions
Is 0.8 g/kg of protein enough to build muscle?
In the trial above, the 0.8 g/kg group didn’t gain significant muscle in four weeks, while the 1.5 g/kg group did. The ISSN recommends 1.4–2.0 g/kg for people who train.
Is more than 1.6 g/kg useless?
For lean mass gains in the meta-analysis, no extra benefit showed up above about 1.62 g/kg. Higher intakes may still help in some cases, such as dieting, and the ISSN gives higher ranges for that.
Do I need whey?
No. The trial used whey, but the ISSN calls supplements a practical way to meet your numbers. Food works too.
Next steps
Pick a daily target near 1.6 g/kg, spread it over several meals, and keep lifting. Check with a clinician first if you have kidney or other medical conditions.
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