How much protein do athletes actually need?

Protein is the most talked-about nutrient in sport, and also the most oversimplified. Old-school advice says hit the RDA and you're covered. Modern marketing says more protein, more often, always wins. Both are wrong.

Requirement vs recommendation

When an athlete asks "how much protein do I need?", they're not asking what it takes to avoid deficiency. They're asking what it takes to recover harder, adapt faster, and perform better. That's a different question.

The 0.8 g/kg/day RDA everyone quotes was never built for athletes. It came from nitrogen balance studies aimed at the general population's minimum needs. Fine for avoiding deficiency. Wrong target if you train.

What actually happens to the protein you eat

Not every gram you eat becomes muscle. Protein breaks down into amino acids, gets absorbed, and then goes one of three ways: built into muscle, burned for energy, or excreted as waste. Eating more doesn't automatically mean building more. What matters is how much of what you eat actually triggers muscle protein synthesis, driven by amino acid availability, delivery to muscle, and the signalling pathways (mTOR especially) that switch synthesis on. Leucine is the key trigger here, not just a building block.

Why "20 grams" became gospel

Classic dose-response studies in young, resistance-trained men found muscle protein synthesis climbed with protein intake up to about 20 g, then flatlined. Egg protein studies showed it. Whey studies backed it up. Beyond 20 g, the extra amino acids just got oxidised or excreted. The takeaway stuck: 20 g post-workout, job done.

It was a useful rule. It was never the whole story.

The ceiling moves

Later research blew a hole in the "20 g is enough" rule. A Maastricht study using whole-body resistance training compared 25 g against 100 g of protein, and the bigger dose extended both the size and duration of the muscle-building response. Another study found 40 g of whey outperformed 20 g after full-body training.

The pattern: the original 20 g studies used leg-only exercise. Work more muscle, and you likely need more protein to max out the response. The real question isn't "is 20 g enough?" It's "enough for what, and for whom?"

Scale it to bodyweight, not a flat number

A 50 kg gymnast and a 110 kg rower shouldn't get the same protein advice. Pooled dose-response data gives a much better working number: roughly 0.24 g/kg per serving on average, with 0.30 g/kg as a sensible upper target to account for individual variation.

• 50 kg athlete: ~15 g per serving
• 70 kg athlete: ~21 g per serving
• 100 kg athlete: ~30 g per serving

Far more useful than telling everyone the same number regardless of size.

Does the type of exercise matter?

Yes. After endurance exercise, around 30 g of protein was enough to maximise both muscle and mitochondrial protein synthesis in trained men, proof that protein isn't just a strength-athlete concern. There's also early evidence that sex matters: in resistance-trained women, 30 g of whey maximised the response after whole-body training. Data from young men doesn't automatically transfer to every population.

Daily intake beats obsessing over one shake

Per-meal targets matter, but athletes live across whole days, not one post-workout window. For weight-stable athletes focused on recovery and adaptation, the evidence points to 1.3–1.6 g/kg/day, with 1.6 g/kg/day a solid working target. Pushing well past that doesn't buy extra muscle in weight-stable conditions. More protein isn't automatically better.

Cutting weight? The target shifts up

This is where higher intakes earn their place. If you're in a calorie deficit and trying to hold onto muscle while losing fat, the picture changes. In men, around 2.4 g/kg/day during a significant deficit preserved far more lean mass than a moderate intake. Similar results show up in women. So during a genuine cut, the target moves to roughly 2.0–2.4 g/kg/day. Context decides the number: weight-stable, gaining, or cutting all call for different targets.

The kidney and bone myths

High protein diets damaging kidneys or bones in healthy people isn't supported by the evidence. That concern applies to people with existing kidney disease, not healthy, training athletes. If you're going to argue against piling on protein, argue that it doesn't add extra benefit in some contexts, not that it's dangerous. Fear isn't a reason. Lack of upside is.

Bottom line

• Stop using the RDA as a performance target. It was never built for that.
• "20 g is enough" was a useful starting point, not a universal rule.
• A sensible working target: ~0.3 g/kg per meal, ~1.6 g/kg/day for most weight-stable athletes.
• Cutting weight and want to hold onto muscle? Push to 2.0–2.4 g/kg/day.
• More isn't always better. But sometimes more is exactly right. It depends on the context: your bodyweight, your training, and your goal.

Source: lecture by Oliver Witard on athlete protein requirements.