Recommendations range from the official daily allowance of 0.8 grams per kilogram to gym advice of well over two, a difference of nearly three times. Both sides cite research.
What does the actual evidence support, and where does the disagreement come from?
Accepted Answer
The disagreement mostly comes from the two sides answering different questions.
The 0.8 figure is the amount needed to avoid deficiency in a sedentary adult. It was never intended as the amount that maximises training adaptation, and quoting it against lifters compares a floor with a ceiling.
The best evidence for trained people doing resistance work points to roughly 1.6 grams per kilogram per day, with the benefit flattening out by about 2.2. Morton's 2018 meta analysis is the usual reference for that.
Above that there is no measured additional benefit for muscle, which is where the gym advice overshoots. It is not harmful for healthy kidneys, it is simply not doing anything.
One qualification that changes the number for some people: it should be scaled to lean mass or to target weight rather than current weight.
For someone carrying a lot of fat, grams per kilogram of total body weight overstates the requirement substantially, because fat tissue is not what you are feeding.
The other case is a calorie deficit. Protein requirements go up while dieting, because you are trying to keep muscle while in a state that encourages losing it, so the upper half of that range makes sense there even though it does not otherwise.
Distribution matters much less than people think. Total daily intake is what the evidence supports; the idea of a strict 30 gram per meal ceiling is not well supported.
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