How much protein you actually need to build muscle

Protein is the only macronutrient the body cannot stockpile for later. That's why it attracts so many myths: "more is always better," "muscles won't grow without 200 grams a day," "protein powder is essential." The science of recent years lets us replace these slogans with concrete numbers.

What the key meta-analysis showed

The pivotal study is the systematic review and meta-analysis by Robert Morton and colleagues, published in the British Journal of Sports Medicine in 2018. The authors pooled 49 studies involving more than 1,800 people who trained with weights.

The conclusion was sobering: gains in lean (fat-free) mass from protein supplementation plateaued at an intake of about 1.62 grams per kilogram of body weight per day (95% confidence interval — from 1.03 to 2.20 g/kg). Anything eaten beyond that added no further muscle mass.

Why "more" doesn't mean "better"

Muscle protein synthesis is a process that saturates. The body can only use a limited amount of amino acids to build tissue per unit of time; the rest is burned for energy or oxidized. So beyond a certain threshold, each additional serving of protein works not on your muscles but on your supplement bill.

At the same time, the upper bound of the confidence interval in Morton's study reaches 2.2 g/kg — meaning that for some people, especially experienced athletes, the optimum may be above average. More recent reviews (2024) note that in trained individuals the benefit of protein more often plateaus closer to 2.0 g/kg. But even the upper estimates are a long way from "eat as much as you can."

What this looks like in practice

For a person weighing 75 kg, Morton's threshold is about 120 grams of protein per day. That's achievable with ordinary food without a single scoop of powder: a couple of eggs, a portion of cottage cheese, chicken breast, fish, legumes, Greek yogurt. A protein shake is a convenient tool to top up your intake, not a magic catalyst.

Distribution matters too. Most studies agree that it makes sense to split your daily target across 3-4 meals of 0.3-0.4 g/kg each, rather than gorging on it all in one sitting. This keeps protein synthesis steady throughout the day.

When you should raise your targets

There are situations where it makes sense to stay at the upper end of the range or even slightly above it. The first is a calorie deficit: when you're losing weight, higher protein helps preserve the muscle the body would otherwise start to "break down" for energy. The second is age: over the years anabolic resistance develops, muscles respond less well to amino acids, so older people are often advised to eat more protein than younger ones. The third is a high training volume in experienced athletes.

A separate question is the source. For muscle protein synthesis, what matters is not only the total amount of protein but also the amount of leucine — the "switch" amino acid. Animal sources (eggs, dairy, meat, fish) are richer in leucine, so on a plant-based diet the overall protein target is usually raised and foods are combined more carefully to cover the amino acid profile. That doesn't make plant protein "worse" — it just requires a little more attention to variety.

What the numbers don't override

Protein is a necessary but not sufficient condition for growth. Without progressive overload (gradually increasing weights or volume) and without enough sleep, even a perfect protein intake won't turn into muscle. Protein is the building material; the stimulus to build comes from training, and the body does the building during recovery. So chasing extra grams of protein while training chaotically and skimping on sleep is a classic case of misplaced priorities.