How much protein do you actually need?
The official number is 0.8 grams per kilogram of body weight. It is also, for most people reading this, the wrong number — because of what it was designed to do.
The short answer
If you don't want the reasoning, here is the range most of the evidence lands on:
- Sedentary adult, no particular goal: 0.8–1.0 g per kg of body weight per day.
- Training regularly, want to build or keep muscle: 1.4–2.0 g/kg.
- Losing weight and trying to keep muscle: 1.6–2.4 g/kg — the leaner you already are, the higher.
- Over about 60: 1.0–1.2 g/kg, higher if you're active or recovering from illness.
For a 75 kg person who lifts a couple of times a week, that's roughly 105–150 g a day. Most people who guess land well below that.
Why 0.8 g/kg is a floor, not a target
The figure you see on nutrition labels and in government guidance — 0.8 g/kg in the US, 0.83 g/kg from the European Food Safety Authority and the WHO — comes from nitrogen balance studies. Those studies asked a specific question: what is the minimum intake at which a healthy adult doesn't slowly lose body protein?
That's a deficiency threshold. It's set to cover about 97.5% of the population's minimum requirement, in the same way the recommended intake for vitamin C is set to prevent scurvy rather than to make you thrive. It was never designed to answer "how much protein makes me strongest", or "how much helps me keep muscle while I diet".
The distinction that matters: "enough to avoid deficiency" and "enough for the outcome you want" are different questions. The RDA answers the first one well and the second one not at all.
This is also why the RDA and the sports-nutrition numbers can both be correct without contradicting each other. They're measuring different things.
If you train
The International Society of Sports Nutrition's position stand recommends 1.4–2.0 g/kg/day for building and maintaining muscle in people who exercise — roughly double the RDA.
The most useful single piece of evidence here is a 2018 meta-analysis by Morton and colleagues in the British Journal of Sports Medicine, which pooled 49 studies of resistance training with protein supplementation. Two findings are worth carrying around:
- Extra protein does increase muscle and strength gains from resistance training. The effect is real and consistent.
- The benefit plateaus at around 1.6 g/kg/day. Above that, the average additional gain gets very hard to detect.
The confidence interval around that plateau extended to about 2.2 g/kg, which is why you'll see people recommend that higher figure as insurance. Both are defensible. What isn't defensible is the implication of most supplement marketing — that there's meaningful benefit at 3 or 4 g/kg. There's no good evidence for it.
If you're losing weight
This is the situation where protein intake matters most, and it's the one people most often get wrong.
When you eat fewer calories than you burn, your body draws on stored energy — and some of what it breaks down is muscle, not just fat. Higher protein intake, combined with resistance training, substantially reduces how much of your loss comes from lean tissue. This is why crash diets so often leave people lighter but visibly softer.
Two other things happen to work in your favour:
- Protein is the most satiating macronutrient. A high-protein meal keeps you full longer than an equivalent number of calories from fat or carbohydrate, which makes the deficit easier to sustain.
- It has the highest thermic effect. Roughly 20–30% of the energy in protein is spent digesting and processing it, against about 5–10% for carbohydrate and 0–3% for fat. This is a genuine effect, but it's a rounding error against total intake — worth knowing, not worth planning around.
The leaner you already are, the more aggressive the recommendation gets, because there's less fat available and the body is more inclined to take the difference from muscle.
If you're older
Adults lose muscle mass steadily from around their forties onward — sarcopenia — and the consequences arrive late, as falls, frailty and lost independence.
Part of the cause is anabolic resistance: older muscle responds less strongly to a given dose of protein. The same 20 g that triggers a solid muscle-building response in a 25-year-old produces a weaker one at 70. The practical answer is more protein per meal, not just more per day.
Expert groups including the PROT-AGE study group and ESPEN recommend 1.0–1.2 g/kg for healthy older adults, rising to 1.2–1.5 g/kg for those who are active or recovering from illness or injury. This is one of the clearer cases where the RDA is actively unhelpful.
Is more protein bad for your kidneys?
This is the most persistent myth in the area, so it's worth being precise.
In people with existing kidney disease, protein intake genuinely does need managing, and that's a matter for their doctor. The myth is the extrapolation from that to healthy people.
In people with healthy kidneys, controlled trials of high-protein diets have not shown harm to kidney function. A 2018 meta-analysis by Devries and colleagues examined this directly and found no adverse effect on glomerular filtration rate. Higher protein intake does raise GFR somewhat, but that appears to be normal adaptation to a greater workload rather than damage — in the same way that exercise raises your heart rate without harming your heart.
To be clear: if you have kidney disease, liver disease, or have been told to limit protein for any reason, none of the above applies to you. Follow your doctor's guidance rather than a website's.
Picking your number
The precision people chase here is mostly wasted. The difference between 1.6 and 1.8 g/kg matters far less than the difference between your target and what you actually eat — and almost nobody knows what they actually eat until they measure it for a fortnight.
So a practical approach:
- Pick a round number from the ranges above. For most active people, body weight in kg × 1.6, rounded to the nearest 10, is a perfectly good target.
- Track it for two weeks without changing anything. The gap between what you assumed and what you eat is usually the whole story.
- Close the gap with food first. Adjust after a month, not after three days.
If your current intake is 70 g and your target is 130 g, the useful question isn't whether the target should be 125 or 140. It's which meals can carry another 20 g.
Two weeks of honest data
PRO.TEIN tracks one number and turns each day into a square. It takes seconds a meal, which is the only reason people keep doing it past week one.
Where these numbers come from
The figures above draw on: the US Institute of Medicine's Dietary Reference Intakes and the EFSA Panel on Dietetic Products' reference values for the RDA; the International Society of Sports Nutrition position stand on protein and exercise; Morton et al. (2018), British Journal of Sports Medicine, for the meta-analysis and the 1.6 g/kg plateau; Devries et al. (2018), Journal of Nutrition, for kidney function; and the PROT-AGE study group and ESPEN guidance for older adults.
This is general information, not medical advice. It can't account for your circumstances. If you have kidney or liver disease, diabetes, are pregnant or breastfeeding, or are managing any medical condition, your protein needs may differ substantially — speak to a doctor or registered dietitian before changing your diet.