How to set a protein target

The Recommended Dietary Allowance for protein is 0.8 grams per kilogram of body weight. For a 75 kg adult that is 60 grams a day. It is also close to irrelevant if you train, and the confusion between those two facts is the single most common error in protein advice.

The RDA answers a different question

An RDA is set to meet the requirements of 97 to 98 per cent of healthy people in a group. It is a deficiency-prevention threshold: the amount below which you start to see problems.

That is a floor. It is not an optimum, and it was never claimed to be one. The Institute of Medicine derived it from nitrogen balance studies — measuring the point at which protein intake matches protein loss — in sedentary adults.

Asking “is the RDA enough protein?” therefore has two answers depending on what you mean. Enough to avoid deficiency? Yes, for most people. Enough to support muscle gain, or to preserve lean mass in a deficit, or to keep an older adult’s muscle from declining? Different question, different evidence, different number.

What the evidence supports for training

The 2016 joint position stand from the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine puts athletes at 1.2 to 2.0 g/kg, varying with training type and phase.

For resistance training specifically, the most useful single number comes from Morton and colleagues’ 2018 meta-analysis in the British Journal of Sports Medicine. Pooling 49 studies, they found gains in lean mass from protein supplementation plateaued at around 1.6 g/kg — beyond which more protein produced no further measurable benefit.

That figure is worth reading carefully. The confidence interval extended to roughly 2.2 g/kg, meaning the true plateau could sit meaningfully higher than the point estimate. So 1.6 is a reasonable target and 2.2 is not excessive; anywhere in that band is defensible.

For endurance training the requirement is lower but still above the RDA, around 1.2 to 1.4 g/kg, reflecting oxidation of amino acids during prolonged exercise and repair afterwards.

When to go higher

Two situations justify pushing toward the upper end.

Training in a calorie deficit. When energy is short, the body is more willing to break down lean tissue. Helms and colleagues reviewed protein intake in resistance-trained lean athletes during restriction and concluded that intakes toward 2.3 to 3.1 g/kg of lean mass were appropriate — which for most people translates to roughly 2.0 to 2.4 g/kg of total body weight. Higher protein also helps with fullness, which makes a deficit easier to hold.

Older adults. Muscle protein synthesis becomes less responsive to a given dose of protein with age — anabolic resistance. Several groups recommend 1.0 to 1.2 g/kg as a minimum for adults over 65, above the general RDA, specifically to slow sarcopenia.

Total body weight or lean mass

At an ordinary body composition it barely matters; the two bases give similar answers.

At a high body fat percentage it matters a lot. Protein requirements track lean tissue, and fat tissue has minimal protein turnover. Scaling to total weight at 40 per cent body fat inflates the target substantially — you are budgeting protein for tissue that does not need it.

The rule of thumb: if your body fat is roughly under 25 per cent for men or 32 per cent for women, use total weight. Above that, use lean mass and aim for around 2.0 to 2.4 g/kg of it. The protein calculator offers both, and you can get a lean mass figure from the body fat calculator.

Distribution across the day

Total daily intake does most of the work. Distribution is a smaller effect, but it is real.

Muscle protein synthesis responds to a dose of protein in a roughly saturable way — somewhere around 0.4 g/kg per meal appears to maximise the response in most people, which is 30 grams for a 75 kg person. Beyond that, the extra amino acids are still used, just not for an additional synthesis spike.

The practical implication is modest: three or four meals containing meaningful protein beat one enormous serving and two without. It is not worth setting alarms for, and it matters far less than hitting the daily total.

Is high protein safe

For people with healthy kidneys, controlled trials at these intakes have not shown harm. Studies following resistance-trained subjects at 2.5 to 3.3 g/kg for months found no adverse changes in kidney or liver markers.

The concern originates with people who already have kidney disease, for whom protein restriction is sometimes prescribed clinically. That is a real medical situation, and extrapolating from it to healthy people is where the myth came from.

If you have kidney problems, this is a question for your doctor, not a calculator.

A worked target

For a 75 kg person doing resistance training three or four times a week, eating at maintenance:

• RDA: 60 g — the deficiency floor, not a target
• Plateau figure at 1.6 g/kg: 120 g
• Upper end at 2.2 g/kg: 165 g

120 grams is the sensible target. In food terms that is roughly a chicken breast, a tin of tuna, a large serving of Greek yoghurt and a couple of eggs across a day — achievable without supplements, though a shake is a convenient way to close a gap.

If the same person moves into a deficit, pushing toward 150 grams is well supported, and the extra fullness is a practical benefit rather than just a theoretical one.

What this costs you

Protein is the most satiating macronutrient per calorie, which is an advantage in a deficit. It is also the most expensive per gram and the most limiting on food choice, which is a real cost.

The macro calculator sets protein per kilogram first, then fat as a share of energy, then gives carbohydrate the remainder — because that is the order in which the evidence is strong. Protein has a defensible target, fat has a published floor of 20 per cent of energy, and carbohydrate is where the body is most flexible.

If a split leaves you with no carbohydrate at all, the protein target is too high for the calorie level, not the other way around.