How much protein you need at your weight, and when more pays off

The official protein number is a floor rather than a target. It comes to about 56 grams a day for someone who weighs 70 kg.¹ Above that, extra protein pays off mainly if you are lifting weights or losing weight.¹

What 56 grams looks like on a plate

Grams of protein are not grams of food. A chicken breast is roughly 30 grams of protein, a large egg about 6, a pot of Greek yoghurt about 15, a cupped handful of cooked lentils about 9. So the official floor is a chicken breast, a yoghurt and two eggs across a day, with the rest arriving unnoticed in bread, rice and milk.

That floor scales with body weight, because bigger bodies hold more muscle to maintain. At 60 kg it is about 48 grams; at 90 kg, about 72.¹

Where the official number comes from

Every official protein figure comes from the same experiment. Feed someone a known amount of protein. Collect what leaves the body. Find the intake where losses stop outrunning intake.

The largest reanalysis of those experiments put the steady point at 104.2 mg of nitrogen per kilogram per day.³ That is about 0.65 grams of protein per kilogram, or 46 grams for a 70 kg adult, a little below the 0.8 on the label.

That experiment answers a narrower question than the label suggests. It finds the intake at which you stop running down your own tissue. It says nothing about the intake at which you do best. Not being in deficit and thriving are different things, and only the first one was ever measured.

There is a second catch. That number is an average. The figure printed on labels sits above it deliberately, so that it covers almost everybody rather than half of everybody. It reads like a target. It is closer to a minimum.

A newer method puts the floor higher

Researchers now have a second way to ask. Feed a labelled amino acid and measure how much of it the body burns instead of building into protein. When burning stops falling, the body has what it needs.

Run both methods side by side and they disagree. In people who do not train, the newer method landed 36% higher: 0.88 grams per kilogram a day against 0.64.² For our 70 kg person that is 62 grams instead of 45.

Nobody has settled which method is right. What the disagreement establishes is that a number everyone treats as a fixed fact about human bodies moves by about a third depending on how you measure it.

When eating more actually buys you something

Above the floor, protein stops being about deficiency and starts being about muscle. And there the answer depends entirely on what else you are doing.

One analysis compared people eating above the allowance against people eating at it. Averaged across everyone, the extra protein was worth 0.32 kg of lean mass. Split by circumstance, that average falls apart. In people losing weight it preserved 0.36 kg. In people lifting weights it added 0.77 kg. In people doing neither it was worth 0.08 kg, with a range that runs from slightly negative to slightly positive — which is to say nothing at all.¹

Extra lean mass from protein above the allowance, kg0 = no effect

While lifting weights+0.77 (0.23 to 1.31)

While losing weight+0.36 (0.06 to 0.67)

Doing neither+0.08 (-0.59 to 0.75)

That is the whole practical rule. Protein above the floor is a lever that only moves when something else is pulling on it.

The by-weight numbers people quote come from the same place. Extra protein showed a clear effect on lean mass in adults over 65 eating 1.2 to 1.59 grams per kilogram a day, and in adults under 65 eating 1.6 or more while doing resistance training.⁴ For a 70 kg lifter under 65, that is about 112 grams a day.

The size of the prize

It is worth knowing how big these effects are before reorganising your shopping.

In a review of 65 trials, protein supplements improved lean body mass by 0.62 kg in adults and 0.46 kg in older adults.⁵ Grip strength did not move. Leg press strength did not move.

Half a kilogram of lean mass is a real effect. It is also a small one. It is unlikely to be visible in a mirror, and it is not what supplement marketing implies.

Older bodies respond differently

Age does not change how much protein you need to stay out of deficit. The nitrogen data found no difference between adults under 60 and over 60.³ What changes is what protein can do once muscle is already being lost.

In adults averaging 50 and older, protein on its own moved nothing measurable. Add resistance training and it did: appendicular lean mass rose 0.54 kg and grip strength 1.71 kg.⁶ The gains concentrated in the frailest participants.

In people who already meet the clinical definition of muscle loss, protein did more on its own. Whey raised muscle mass index and walking speed even without training.⁷

So the older you are, the more the answer is "protein plus movement", and the less it is "protein".

What this does not settle

The foundation is old and cannot be rebuilt. The reanalysis notes that new balance studies have become hard to run for ethical and practical reasons, so every official figure rests on a fixed body of older work.³ The 30% gap between the two measurement methods has never been closed by a trial designed to close it.²

The training result that looks most impressive rested on three comparisons.¹ Most older-adult trials carried some risk of bias, and the analysis could not find a dose-response at all — the per-kilogram numbers are thresholds noticed across studies, not doses tested against each other.^4,6

And nobody has followed adults for years on a weight-scaled protein target against a flat one to see who can still stand up from a chair unaided at the end.