Three different protein numbers circulate, and they answer three different questions. The UK reference intake is 0.75g per kilogram of body weight per day, which is the amount that keeps a sedentary adult out of deficiency. The figure that comes up in gyms is closer to double that. Older adults recovering from illness or surgery sit somewhere in between, for reasons that have nothing to do with building muscle. This page sets out where each number comes from, which one applies to you, and what it looks like on a plate.
Protein demand rises while a surgical wound and the muscle around it are rebuilding, which is part of why PhysioHub's guide to post-surgery rehabilitation puts so much weight on what happens in the first six weeks.
The UK reference nutrient intake for protein is 0.75g per kilogram of body weight per day. For a 70kg adult that is about 53g. This figure was set to cover the requirements of most healthy, largely inactive people, so it is a floor rather than a target.
For anyone doing regular resistance training with the aim of gaining muscle, the research supports around 1.6g per kilogram per day, roughly 112g for that same 70kg adult. The next fold covers where that figure comes from and how firm it is.
For adults over about 65, the recommendation rises to 1.0 to 1.2g per kilogram per day even without training, and higher again during illness or recovery. The PROT-AGE position paper, published in the Journal of the American Medical Directors Association in 2013, sets that range on the basis that ageing muscle responds less strongly to a given dose of protein and needs more of it to trigger the same repair.
Use your actual body weight unless you are carrying a lot of excess weight, in which case these multipliers overshoot. A reasonable adjustment is to calculate from a weight in the middle of a healthy range for your height.
The most useful single piece of evidence is a 2018 systematic review and meta-analysis in the British Journal of Sports Medicine by Morton and colleagues, which pooled 49 trials and 1,863 participants, all of them doing prolonged resistance training with or without extra protein.
Two findings matter. Extra protein produced real but modest gains: about 2.49kg on one-repetition-maximum strength and 0.30kg of fat-free mass across the pooled trials. And the benefit stopped at a total intake of about 1.62g per kilogram per day, with the upper edge of the statistical uncertainty around that estimate reaching 2.2g. Above that, more protein bought nothing extra.
That plateau is the practical message. Someone eating 1.6g per kilogram and training properly is already getting everything protein has to offer, and pushing to 3g per kilogram adds cost rather than muscle. The review also found the effect shrank with increasing age and was larger in people who were already trained, which is a reminder that protein amplifies a training stimulus rather than creating one.
Rough protein content of common UK foods, which is enough precision for this purpose:
The 70kg gym-goer aiming at 112g gets there with eggs and yoghurt at breakfast, a tin of tuna and beans at lunch, chicken and lentils at dinner, and milk through the day. It is achievable from food, and most people who fall short do so at breakfast and lunch rather than dinner.
Spreading intake across three or four meals of 20 to 40g each is modestly better than loading it all into the evening, because each meal has to clear a threshold to switch on muscle protein synthesis. The size of that effect is small next to the daily total, so fix the total first.
Three situations raise protein requirements for reasons unrelated to building muscle.
Ageing muscle. From around the fourth decade, muscle mass declines steadily, and the ageing muscle responds less to a given protein dose. That is why the PROT-AGE range starts at 1.0g per kilogram and why the same group recommends pairing it with resistance exercise. Protein without loading in an older adult mostly gets used for something else.
Immobilisation and disuse. A limb in a cast or a week in a hospital bed loses muscle quickly, and the loss is fastest in the first fortnight. Protein intake does not prevent it, though it slows the rate, and it supports the rebuild once loading resumes. Our article on rehab after a cast comes off covers what that rebuild involves.
Surgery and wound healing. Requirements rise while tissue is being laid down, and appetite often falls at exactly the same time, which is the awkward combination. Aiming at the higher end of the range in the weeks after an operation is sensible, and liquid sources are useful when appetite is poor.
The claim that a protein shake has to be drunk within 30 minutes of training has been repeated so often it now sounds like physiology. The evidence for a narrow window is weak. Total daily protein intake dominates the outcome, and the muscle stays sensitised to protein for many hours after a training session.
The related claim that the body can only absorb 20 to 30g of protein at a sitting confuses absorption with use. Larger doses are absorbed perfectly well. A larger dose produces a longer, flatter rise in muscle protein synthesis rather than a proportionally bigger spike, which is why spreading intake helps a little, and why a 60g meal is not wasted.
If a shake after training makes hitting the daily total easier, that is a good enough reason to have one. The timing is a convenience rather than a mechanism.
For healthy adults with normal kidney function, intakes in the range discussed here have not been shown to cause kidney damage. The concern originates in advice given to people who already have chronic kidney disease, where protein restriction is sometimes part of treatment, and it was generalised from there. Anyone with known kidney disease should take protein advice from their own clinical team rather than from a training article.
The real costs of a very high intake are practical. Protein is filling, so a large target can crowd out carbohydrate that fuels training and fibre that does everything else. It is expensive. And past the plateau it buys nothing measurable, which makes 3g per kilogram an odd thing to spend money and appetite on.
The belief that arrives with this question is usually the anabolic window: that the protein has to land within half an hour of the last set or the session is wasted. What actually shows up when someone writes down a normal week is a different problem entirely, and it is nearly always the same one. Breakfast is toast or cereal, lunch is a sandwich, and two thirds of the day's protein arrives after 7pm.
That matters for rehabilitation more than for muscle gain. Someone rebuilding a quadriceps after knee surgery, or an older adult regaining strength after a fall, is asking their body to lay down tissue on a schedule, and the raw material has to be there through the day when the loading happens. In the Uckfield clinic the fix is usually two small changes at breakfast and lunch rather than a supplement plan, and it costs less than a tub of powder.
If you want a strength programme built around what your body is currently able to recover from, our 1:1 rehab and strength training sessions are where that is put together.
How much protein do I need a day?
Between 0.75g and 1.6g per kilogram of body weight, depending on what you are asking of your body. 0.75g per kilogram is the UK reference intake for a healthy inactive adult, 1.0 to 1.2g applies over about 65, and around 1.6g is the point at which extra protein stops adding to gains from resistance training.
How much protein to build muscle?
About 1.6g per kilogram per day alongside a resistance training programme. The 2018 BJSM meta-analysis found no further benefit above roughly that intake.
Do I need a protein shake?
No. Powder is a convenient way to hit a daily total that is hard to reach from meals alone, and it has no advantage over food when the total is the same.
Is too much protein bad for your kidneys?
In healthy adults with normal kidney function, there is no good evidence of harm at these intakes. The advice to restrict protein applies to people who already have chronic kidney disease.
Does protein timing matter?
Only a little. Spreading intake across three or four meals is slightly better than concentrating it in the evening. The 30-minute window after training is not supported by the evidence.
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