How Much Protein Do You Actually Need?

Where 0.8 g/kg comes from, and what it is for

The Recommended Dietary Allowance for protein is 0.8 grams per kilogram of body weight per day. It is worth understanding how that figure was produced, because the derivation explains exactly what it can and cannot tell you.

The RDA was established largely from nitrogen balance studies: feed people varying amounts of protein, measure nitrogen in versus nitrogen out, find the intake at which they break even. Take that average requirement, add two standard deviations so it covers roughly 97.5% of healthy adults, and you get 0.8 g/kg.

Two consequences follow. First, this is a population safety margin against deficiency, in the same family as the RDA for vitamin C — the amount that stops something going wrong, not the amount that makes something go right. Second, nitrogen balance measures whether you are losing body protein. It says nothing about whether you are building muscle, recovering from training, or preserving lean mass into your seventies. Those are different questions, and they have different answers.

Reviewers have also noted that the nitrogen-balance method tends to underestimate requirements, and studies using the newer indicator amino acid oxidation technique generally arrive at higher figures. The RDA is a floor, and possibly a slightly low one.

The ceiling for muscle: about 1.6 g/kg

The most useful single number in this field comes from a 2018 systematic review and meta-analysis by Morton and colleagues in the British Journal of Sports Medicine, pooling 49 studies and 1,863 participants on protein supplementation during resistance training.

The finding: protein intake was associated with greater gains in fat-free mass, and the effect plateaued at approximately 1.6 g/kg/day. Beyond that point, more protein produced no additional gain in lean mass. The upper bound of the confidence interval reached roughly 2.2 g/kg, which is where the commonly quoted "up to 2.2" figure comes from — it is a statistical safety margin, not a demonstrated benefit.

Put in practical terms:

Body weight	RDA (0.8 g/kg)	Training target (~1.6 g/kg)
55 kg / 121 lb	44 g	88 g
70 kg / 154 lb	56 g	112 g
85 kg / 187 lb	68 g	136 g
100 kg / 220 lb	80 g	160 g

A second, sometimes overlooked, result from the same analysis: the benefit of supplemental protein shrank as participants got older and was larger in trained than untrained individuals. Untrained beginners gain muscle readily on almost any adequate intake; the protein variable matters more once the easy adaptation is spent.

One nuance for anyone dieting. When calories are restricted, protein requirements go up, not down, because protein is being drawn on for energy and because preserving lean mass in a deficit is harder. Intakes toward the upper end of the range — and in some athlete studies beyond it — are reasonable during weight loss, and protein's effect on satiety helps independently.

Older adults: the requirement rises

This is the part of the protein story with the clearest public-health stakes, and it runs opposite to intuition.

Ageing muscle exhibits anabolic resistance: the same dose of protein produces a smaller muscle-protein-synthesis response in a 75-year-old than in a 25-year-old. To get an equivalent effect you need more protein, and you need more of it per meal, because the response appears to be threshold-driven rather than purely dose-additive.

Meanwhile, appetite tends to fall with age, and protein-rich foods are often the ones dropped first — meat becomes harder to chew, cooking for one becomes less appealing. The result is a population whose requirement is rising while their intake is falling. That gap is one contributor to sarcopenia, the progressive loss of muscle mass and strength that eventually underlies frailty, falls and loss of independence.

Expert groups such as the PROT-AGE study group and ESPEN have recommended intakes in the region of 1.0 to 1.2 g/kg/day for healthy older adults, rising toward 1.2–1.5 g/kg with illness or when combined with resistance training. Research comparing 1.6 g/kg against the 0.8 g/kg RDA in older adults doing resistance exercise has favoured the higher intake for muscle mass and strength.

The critical caveat, which the supplement industry consistently buries: protein without resistance training does very little for muscle in older adults. The evidence supports the combination. Protein is the raw material; training is the signal. Supplying material with no signal mostly produces expensive urine.

Timing, distribution, and quality

Three secondary questions, in order of how much they actually matter.

Total daily intake is the dominant variable, by a wide margin. If you get one thing right, get the daily total right.

Distribution has a modest effect. Spreading protein across three or four meals of roughly 25–40 g each appears somewhat better for muscle protein synthesis than concentrating it in one large evening serving — the effect is real but small compared with hitting the total. It matters more for older adults, who may need a larger per-meal dose (often cited around 25–30 g, with adequate leucine) to clear the anabolic-resistance threshold.

Timing relative to training matters least. The "anabolic window" of 30 minutes post-workout was extrapolated from studies that also manipulated total intake, and better-controlled work has found the window is measured in hours, not minutes. Eating protein at some point reasonably near training is sensible; setting an alarm is not.

On quality: animal proteins are complete and leucine-rich, and leucine is the amino acid that most strongly triggers muscle protein synthesis. Most plant proteins are lower in leucine and typically limiting in one essential amino acid — lysine in grains, methionine in legumes. The classic "combine complementary proteins at every meal" advice has been superseded; what matters is variety across the day. Plant-based eaters generally do well by targeting the upper end of the range and including soy, which is complete and leucine-competitive.

The kidney question

This deserves a direct answer because it circulates widely.

In people with healthy kidneys, there is no good evidence that higher protein intakes damage renal function. Systematic reviews of controlled trials in healthy adults, including trials at intakes well above the RDA sustained for months, have not found deterioration in glomerular filtration rate. Higher protein intake does raise GFR — but this is understood as a normal adaptive response to a higher filtration load, not evidence of injury, in the same way that muscles adapting to load is not evidence of damage.

The situation is genuinely different in existing chronic kidney disease, where protein restriction is a recognised part of management in some stages. That is a clinical decision made with a nephrologist.

A more practical concern for most people is displacement. Chasing a very high protein target often means crowding out fibre, fruit and vegetables — which carries real costs that have nothing to do with kidneys. Protein is one variable in a diet, not the whole scoreboard.

What to actually do

• Sedentary, healthy, not elderly: 0.8–1.0 g/kg is genuinely adequate. Most people in developed countries already exceed this without trying.
• Resistance training: aim for 1.4–1.6 g/kg. Going above adds cost and effort for no demonstrated gain in lean mass.
• Dieting while training: the upper end of that range, or slightly above.
• Over 65: 1.0–1.2 g/kg minimum, higher if training or ill — and do the resistance training, because that is what makes the protein matter.

Then stop optimising. Protein is the macronutrient with the clearest evidence and the smallest remaining upside once you are in range. The returns on getting from 1.6 to 2.2 g/kg are, on the current data, indistinguishable from zero — while the returns on the two strength sessions a week are not.

Further reading: The plateau finding is Morton et al., British Journal of Sports Medicine (2018). Older-adult recommendations come from the PROT-AGE study group (Bauer et al., JAMDA, 2013) and ESPEN's guidance on clinical nutrition. Examine's protein intake guide maintains a well-sourced overview.

This article is general information, not medical or dietary advice. If you have kidney disease, liver disease, or are pregnant, protein targets should be set with a clinician.