Optimal Daily Protein Intake for Hypertrophy: What the Meta-Analyses Say

The optimal protein intake for muscle growth is about 1.6 g per kg of body weight per day, with up to 2.2 g/kg (0.7-1.0 g per lb) as a sensible upper target. That comes mainly from one large meta-analysis, and it is the number most nutrition plans on this site are built around.

This article is the evidence breakdown behind that number. If you want the full picture of protein sources, timing and supplements, start with our complete protein guide for hypertrophy. Here we stay on one question: how many grams, and how sure are we?

What did the Morton protein study actually find?

Morton and colleagues pooled randomized controlled trials where people did resistance training for at least 6 weeks and some groups got extra protein. The final set was 49 studies with 1,863 participants (Morton et al., 2018).

Protein supplementation produced small but statistically significant extra gains:

• strength (1RM): +2.49 kg on average
• fat-free mass: +0.30 kg
• muscle fibre cross-sectional area: +310 µm2

Those are modest numbers. Protein does not replace training, it nudges the result. The analysis also found the benefit for fat-free mass was smaller with increasing age and larger in resistance-trained people (+0.75 kg).

Why do people say 1.6 and 2.2 g/kg?

The 1.62 g/kg figure is the average break point. The paper’s open-access full text reports it with a 95% confidence interval of 1.03 to 2.20 g/kg/day. That interval is the source of the “2.2” in 1.6-2.2.

Think of it this way. The data says the plateau most likely sits near 1.6 g/kg, but it could plausibly sit anywhere from about 1.0 to 2.2 depending on the person and the trial. If you eat 1.6 g/kg you are at the best estimate. If you eat 2.2 g/kg you are covering most of the plausible range.

How much protein per day for hypertrophy, by body weight?

Take your weight in kg and multiply. Here is that arithmetic for common body weights.

Prefer an exact answer for your body? Use our free protein calculator.

Do other studies agree with Morton?

Mostly yes, with some useful differences.

Nunes et al. (2022) pooled 74 randomized trials in healthy, non-obese adults. Among people doing resistance training, increasing protein intake modestly improved lean body mass (SMD 0.22, 62 studies, moderate level of evidence). The effect was significant in younger adults eating 1.6 g/kg or more, and in people 65 and over eating 1.2-1.59 g/kg (Nunes et al., 2022). The authors call the gains “small”.

Tagawa et al. (2022) looked at strength rather than size. Across 82 trials, protein only improved strength when combined with resistance training. Strength gains rose with total protein up to about 1.5 g/kg/day, with no further gain after that (Tagawa et al., 2022). Several authors work for Meiji, a Japanese dairy and food company, which is worth knowing when you weigh the result.

The ISSN position stand says 1.4-2.0 g/kg a day is sufficient for most exercising individuals to build and maintain muscle (Jager et al., 2017).

Four sources land in a similar zone: 1.4-2.0 (ISSN), about 1.5 (Tagawa, strength), 1.62 (Morton) and at least 1.6 for younger adults (Nunes).

Why might the numbers differ slightly?

Each analysis asked a slightly different question. Morton looked at fat-free mass in trials with supplementation, Tagawa at strength, and Nunes at lean mass with a wide range of designs. Trials also differ in training experience, age, calorie intake and how protein was measured.

One more honest caveat. Break points from pooled data are statistical estimates, not biological cliffs. The wide confidence interval around the Morton break point is a reminder that individual needs can sit well away from the average. Treat 1.6 as a starting point you test, not a law.

Is more than 2.2 g/kg useful?

For building muscle in people eating at maintenance or in a surplus, trials in this analysis do not show extra growth above roughly 1.6 g/kg. Going well beyond 2.2 g/kg mostly takes up calories and money you could spend on carbs, which fuel training.

There is one important exception, covered next.

Do you need more protein when cutting?

Probably yes. A systematic review of six studies in lean, resistance-trained, energy-restricted athletes concluded needs are likely 2.3-3.1 g per kg of fat-free mass, scaled upward with the severity of the deficit and leanness (Helms et al., 2014). The review was small, and it used fat-free mass rather than total weight. Our guide to high protein while cutting goes through this properly.

What about age, kidneys and other limits?

Age. Morton found the benefit of supplementation on fat-free mass fell as age rose, and Nunes saw benefits in older adults at lower intakes than younger adults. Older lifters have their own considerations, covered in our article on protein needs in older adults.

Kidneys. In people with healthy kidneys, the intakes discussed here are not known to cause harm, but people with kidney disease should not self-prescribe high protein. See our high-protein diet and kidney safety review, and see a doctor if you have any kidney diagnosis, persistent swelling, or abnormal kidney tests.

Per meal. Total daily protein matters most, though spreading it out is practical. See protein distribution across meals, and the idea of a per-meal absorption ceiling.

How to set your own protein target

1. Weigh yourself in kg. Use your goal weight if you carry a lot of body fat.
2. Multiply by 1.6 for your starting number.
3. Multiply by 2.2 for your ceiling.
4. Track your intake for 2 weeks and see where you naturally land.
5. Re-check in 6-8 weeks against strength, waist and body weight trend.

Start with the number you can actually repeat. A common trap is hitting 2.2 g/kg for three days, then drifting far lower the rest of the week.

Hitting 1.6 g/kg on an Indian diet

For a 70 kg vegetarian lifter, 112 g is a real stretch if the day is mostly roti and rice. Build each meal around a main protein: dal or rajma with curd, paneer or tofu, soya chunks, eggs if you eat them, plus a glass of milk or a scoop of whey. Soya chunks and eggs are often the cheapest per gram of protein, though prices vary by city.

A shake is a convenience, not a requirement. Your muscles respond to the daily total, whatever source it comes from. Plant proteins tend to be a bit lower in some essential amino acids, so mixing sources and aiming for the upper half of the range can help. For ideas and budgets, see our Indian high-protein nutrition guide and the budget protein diet, and compare plant vs animal protein.

Need a ready-made meal structure? Try our free diet plan.

Common mistakes when applying the meta-analysis

Treating the break point as a cliff. Eating 1.5 g/kg instead of 1.62 g/kg does not cost you your gains. The curve flattens gradually, so a few grams either way is noise.

Ignoring total calories. The Morton trials were resistance training studies where protein was the variable. If you are eating far too little overall, protein alone will not rescue progress. Sort out calories first with our calorie calculator.

Chasing the number with powder only. A scoop of whey is useful, but a day of three shakes and little real food is harder to sustain. Use food first, then fill the gap.

Assuming the studies were all in advanced lifters. Many participants were not highly trained, and most trials last weeks to a few months. We have much less long-term data on how needs change over years of training, so hold the numbers loosely.

A worked example for a 70 kg lifter

Say you weigh 70 kg and want a starting target. At 1.6 g/kg that is 112 g, and at 2.2 g/kg it is 154 g. Aim for about 120-130 g, which sits comfortably in the middle.

A realistic vegetarian day might look like this: curd with breakfast, dal and paneer at lunch, soya chunks or tofu at dinner, milk or a whey shake after training, and a handful of peanuts or roasted chana as a snack. Each of those contributes a meaningful chunk, and four or five protein-anchored meals gets you there without forcing anything. If you eat eggs or chicken, swap them in. Check labels, since protein per serving varies a lot between brands.

If you are heavier or carrying a lot of body fat, using your goal weight instead of your current weight keeps the target realistic and the numbers from ballooning.

The bottom line

The strongest evidence we have says 1.6 g/kg a day is where extra protein stops adding measurable muscle, and 2.2 g/kg is a reasonable ceiling that covers the uncertainty. These are averages from trials, and trials are short. Hit your number most days, train hard, sleep well, and only adjust if your progress tells you to.