Nutrition, Diet & Fasting - Food foundations
How much protein do you actually need?
One of the few nutrition numbers that comes from a proper meta-analysis rather than a magazine. There is a point above which more protein stops adding muscle, and it has been measured.
Protein is the macronutrient people are least likely to be wrong about in direction and most likely to be wrong about in size. Almost everyone in fitness knows more is better; far fewer know that the research has identified roughly where "more" stops mattering, and that the number is lower than most supplement marketing implies.
The number, and where it comes from
The most-cited analysis is a 2018 systematic review and meta-analysis by Morton and colleagues, pooling data from around 1,800 participants across trials of protein supplementation alongside resistance training. It looked for a breakpoint - the intake above which extra protein produced no further gain in fat-free mass - and found one at approximately 1.6 grams of protein per kilogram of body weight per day.
The confidence interval around that estimate ran from roughly 1.0 to 2.2 g/kg/day, which is wide, and that width is the honest part of the finding. It is why the common practical advice lands at 1.6 to 2.2 g/kg for someone training hard and wanting to be certain they are not the person at the top of the range. What the analysis does not support is the much higher intakes routinely promoted, for which it found no additional benefit.
For scale: a person weighing 80 kg is looking at roughly 130 to 175 grams a day at that range. The UK reference nutrient intake for a sedentary adult is far lower - around 0.75 g/kg - and those two numbers answer different questions. The lower one is about avoiding deficiency; the higher one is about maximising muscle response to training.
The cases where more protein matters most
Two situations shift the number up, and both are under-appreciated. The first is a calorie deficit: when energy is short, protein requirements rise, because adequate protein is one of the main things determining whether weight lost is fat or muscle. Anyone dieting - on any of the diets in this classroom - has more reason to prioritise protein than someone eating at maintenance, not less.
The second is age. Older adults experience anabolic resistance, meaning the same amount of protein produces a smaller muscle-building response than it would in a younger person. Trials in older adults have found meaningfully greater muscle gains at higher protein intakes combined with resistance training than at the standard reference intake. Given that loss of muscle and strength is one of the better predictors of how well someone ages, this is one of the more practically important findings in the classroom.
What matters less than people think
Meal timing and distribution get a great deal of attention and appear to matter far less than total daily intake. The "anabolic window" - the idea that protein must be consumed within a short period after training - has not held up well in controlled research; total protein across the day dominates. Spreading intake reasonably across meals is sensible and probably marginally better than one enormous serving, but it is a refinement, not the main lever.
Source matters somewhat. Animal proteins are generally higher in leucine and more complete in essential amino acids, so plant-based eaters typically need somewhat more total protein and more attention to variety to get the same effect. That is a real adjustment rather than a barrier.
Where the evidence stops
The breakpoint comes from trials of supplementation in mostly younger, mostly healthy, mostly resistance-training participants, so extrapolating it to endurance athletes, to people not training, or to clinical populations is an extension of the data rather than a reading of it. The wide confidence interval means individual variation is substantial. And the frequently repeated claim that high protein intake damages healthy kidneys is not supported by the evidence in people with normal kidney function - though existing kidney disease is a genuine exception where intake should be set by a clinician.
Educational content only and not medical advice. Anyone with existing kidney disease should have protein intake advised by a qualified healthcare professional rather than set from general guidance.
Related in this classroom
Sources for this classroom
Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.
