Protein Needs for Muscle Growth: Why 1.6g Per Kilo Is Enough

1.6 g of protein per kilogram of body weight is one of the best-known numbers in sports nutrition.

It is also one of the most widely misread.

1.6 g/kg is neither a magic threshold below which no muscle grows, nor a hard ceiling above which every additional gram is “wasted”.

The number comes from a meta-regression and describes an average point of diminishing additional returns.

For practical purposes, then, a range serves you better than one perfect number.

1.6–2.2 g/kg: what this range actually means

Morton and colleagues analysed 49 studies with 1,863 participants.

Their meta-regression estimated the point beyond which additional protein no longer explained any clear further gain in fat-free mass, on average, at roughly 1.62 g/kg of body weight per day.

The upper confidence limit sat at around 2.2 g/kg.

That is why the range 1.6–2.2 g/kg gets recommended so often today.

The interpretation is what matters, though:

• 1.6 g/kg is not a universal minimum for muscle growth.
• 2.2 g/kg is not a biological ceiling.
• The values describe a population and a statistical uncertainty, not your personal exact requirement.

So this way of thinking about it works well in practice:

1.6 g/kg is a solid target. 1.8–2.2 g/kg buys extra buffer if you want to be on the safe side or have particular circumstances.

Protein table by body weight

For an 80-kg lifter, 160 g a day is therefore not a scientific obligation.

It is a convenient target sitting in the middle of a well-supported range.

Why different sources still name different numbers

It is tempting to explain higher protein recommendations purely as supplement marketing.

Reality is less dramatic.

Different recommendations arise partly because studies and guidelines are looking at different situations:

• building muscle in a calorie surplus
• retaining muscle in a diet
• older adults
• very lean competitive athletes
• total protein versus protein per meal
• animal versus plant protein sources
• body weight versus fat-free mass as the reference

So 1.6 g/kg of body weight in a building context and 2.3–3.1 g/kg of fat-free mass in an aggressive bodybuilding diet can both come from the literature without contradicting each other.

They answer different questions.

How much protein per meal?

The daily total is the biggest lever.

Distribution can be optimised after that.

Schoenfeld and Aragon proposed roughly 0.4 g/kg per meal as a practical guide, spread across several meals.

At 80 kg that would be about:

32 g of protein per meal

This is not a hard absorption limit.

It is a sensible portion that, in many people, supplies enough essential amino acids and leucine to stimulate muscle protein synthesis clearly.

A simple day might look like this:

Whether that comes out at exactly four meals matters less than the daily total.

”The body cannot use more than 30 g” is wrong

Your body does not stop absorbing amino acids after 30 g of protein.

Larger portions get digested and absorbed too.

The better question is:

How much of a meal acutely maximises muscle protein synthesis — and how do I distribute my daily total sensibly?

That is something entirely different from “using” protein.

A larger protein portion can also be used for other tissues, enzymes, hormones and general amino acid metabolism, or be oxidised.

So there is no need to halve a 35-g portion in a panic.

Animal or plant: the differences are small, but not zero

In the fitness world this question usually gets an answer that is too absolute.

Animal protein sources tend on average to offer:

• high digestibility
• plenty of leucine
• a complete profile of essential amino acids

Many plant sources, by contrast, have lower digestibility or less of individual essential amino acids.

That does not make plant protein “bad”, though.

A 2025 meta-analysis found a small advantage for animal sources on muscle mass, while soy showed no relevant difference against dairy protein. Strength gains did not differ significantly overall.

Another meta-analysis from 2026 on acute muscle protein synthesis likewise found only small, uncertain differences, with a somewhat stronger signal in favour of animal proteins in older adults.

In practice:

If you eat mostly plant-based, raise the total a little, use a variety of sources, and pay attention to protein-rich foods with a good EAA profile.

A target closer to 2.0–2.2 g/kg can serve you better there than exactly 1.6 g/kg.

When a bit more protein can make sense

In a calorie deficit

The larger the deficit and the lower your body fat, the more retaining muscle matters.

Which is why higher protein intakes are often recommended for very lean, resistance-trained athletes in a diet.

The well-known recommendation from Helms et al. sits at 2.3–3.1 g/kg of fat-free mass.

But that is deliberately a specialised recommendation for natural bodybuilding contest prep — not a default for anyone who wants to lose a couple of kilos.

As you get older

Older adults often show a smaller acute anabolic response to smaller protein portions.

That argues for eating enough high-quality protein per meal and not setting the daily total at the bottom of the range.

It does not mean everyone over 40 suddenly needs 2.2 g/kg.

On a mostly plant-based diet

Here a somewhat higher total protein intake can offset the lower digestibility and the differences in the amino acid profile of individual sources.

More important than a perfect factor is that the diet as a whole delivers enough protein from a variety of good sources.

Protein timing: relevant, but not dominant

Protein around training is a good idea.

The classic 30-minute countdown is still too tight.

A 2025 meta-analysis looking at direct pre-versus-post comparisons found no relevant difference in fat-free mass.

So if you already ate protein a few hours before training, there is little time pressure afterwards.

If you train after a long fast, on the other hand, the next protein serving becomes more important in practical terms.

The basics on calories, macronutrients and supplements belong in the nutrition guide; here the focus deliberately stays on protein.

Do you need protein powder?

No.

Protein powder is not an anabolic agent in its own right.

It is concentrated food.

Its advantages:

• fast
• easy to portion
• relatively cheap per gram of protein
• practical when normal meals do not cover your needs

If you hit 150 g of protein comfortably through normal food, you do not need to add a shake.

If you are 30 g short, a shake is an easy solution.

Does a lot of protein damage the kidneys?

In healthy people, the sports nutrition literature shows no convincing sign that the high protein intakes typical among strength athletes damage the kidneys.

The qualifier matters:

That does not automatically apply to people with existing kidney disease.

And it makes little sense to derive the opposite claim from it, that arbitrarily high amounts are useful as a matter of course.

If you are already in the 1.6–2.2 g/kg range, additional calories for your training goal are often better distributed across a balanced overall diet.

How to set your own target

You do not need a precise lab formula.

A workable procedure:

1. Start at around 1.6–2.0 g/kg of body weight.
2. If you are in a clear deficit, very lean, or eating mostly plant-based, move towards the upper end.
3. Spread protein across several meals without optimising every portion to the gram.
4. Check that the amount fits your daily life and your total calories.
5. Do not change anything just because one influencer recommends 3 g/kg.

For most healthy people who lift, that is already enough.

Conclusion

The famous 1.6 g/kg is a very good reference point — but not a biological switch.

The best practical summary:

• 1.6 g/kg: already enough for many people to capture most of the available effect
• 1.8–2.2 g/kg: a sensible buffer for individual differences
• more: can make sense in specific situations, but is not automatically better for ordinary muscle growth

Protein matters.

The precision is not in finding the one magic number of grams.

It is in eating enough protein reliably, without making the rest of your diet unnecessarily complicated.

Further reading:

• Nutrition for muscle growth: the complete guide
• Strength training for beginners
• Hypertrophy training guide
• Strength standards: where do you stand?
• Tracking progress with hitPR

Sources

• Morton RW et al. (2018). 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, 52(6):376–384. PubMed 28698222
• Stokes T et al. (2018). Recent perspectives regarding the role of dietary protein for the promotion of muscle hypertrophy with resistance exercise training. Nutrients, 10(2):180.
• Schoenfeld BJ, Aragon AA (2018). How much protein can the body use in a single meal for muscle-building? Journal of the International Society of Sports Nutrition, 15:10.
• Helms ER et al. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11:20.
• Roberts-Molina RJ et al. (2025). Effect of Plant Versus Animal Protein on Muscle Mass, Strength, Physical Performance, and Sarcopenia: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Nutrition Reviews. PubMed 39813010
• Jovanov P et al. (2026). Effects of Plant- vs Animal-Based Proteins on Muscle Protein Synthesis: A Systematic Review With Meta-Analysis. Journal of the Academy of Nutrition and Dietetics. PubMed 42055214
• Yimam A et al. (2026). Long-term effects of plant vs. animal protein supplementation on body composition, muscle strength, physical performance, and cardiometabolic risk factors in adults: a systematic review and meta-analysis. PubMed 41994089
• Luis-Vicente A et al. (2025). Does Protein Ingestion Timing Affect Exercise-Induced Adaptations? A Systematic Review with Meta-Analysis. Nutrients, 17(13):2070. PubMed 40647175