How much protein do you actually need per day?

What 0.8 g/kg is the answer to

The 0.8 grams per kilogram figure quoted everywhere is a recommended dietary allowance, and its definition usually gets dropped in transit: it is the amount that prevents deficiency in almost all healthy adults. It measures adequacy. It says nothing at all about optimal.

Where the number comes from matters. It was derived from nitrogen balance studies, which look for the point where nitrogen in equals nitrogen out, then add a safety margin. Balance does not mean muscle was preserved — you can lose muscle while other lean tissue grows and still balance the books.

For a 70 kg adult, 0.8 g/kg comes to 56 grams a day. A two-egg breakfast, a bowl of yoghurt at lunch and a medium chicken breast at dinner already clears it, which is precisely why using it as a target asks nothing of anyone and therefore gives nothing back.

Why the number rises in a deficit

In a calorie deficit your body covers part of its needs from storage, and storage is not only fat. When protein intake is low and nothing is asking the muscle to stay, a meaningful share of the loss comes out of muscle tissue.

Protein does two separate jobs while you diet. It slows that loss. It also makes the deficit survivable, because a meal with a high protein share produces less hunger a few hours later than the same calories arranged differently — and a diet you abandon in week three has an adherence problem, not a macro problem. We covered how the deficit itself works separately; protein decides which tissue pays for it.

For adults training regularly, the sports nutrition literature generally lands on 1.4–2.0 g/kg. As the deficit deepens and body fat falls, moving toward the top of that range makes more sense, since there is less margin for error the less spare tissue you carry.

Why lean mass is the better basis

Calculating from total body weight inflates the number at higher body fat percentages. Fat tissue does not ask for protein. For someone at 120 kg and 40% body fat, 2 g/kg means 240 grams a day — an absurd figure for the 72 kg of lean mass that actually needs protecting.

If you know your body composition, the range defined in the literature for athletes in a deficit is 2.3–3.1 grams per kilogram of lean mass (Helms et al.). The lower end suits higher body fat; the upper end suits a body already close to lean. The range looks wide because it is personal: of two people with identical lean mass, the one lifting five days a week belongs at the top and the one only walking belongs at the bottom, and the gap between them runs to about 50 grams a day.

Do not know your body fat? Use total weight and remember the answer skews high.

Distribution across meals

The daily total is the number that matters most. It is not the only one. A per-meal threshold of roughly 0.4 g/kg has been described for stimulating muscle protein synthesis (Schoenfeld and Aragon, 2018) — about 28 grams per meal at 70 kg.

Leucine is the mechanism behind that threshold. This amino acid acts like the key that starts synthesis, and roughly 2.5–3 grams of it appear to be needed per meal; 25–30 grams of a quality animal protein delivers that much. Plant sources carry less leucine per gram, so the same trigger asks for a slightly larger portion. Not impossible. Just something to plan for.

Spreading 140 grams across three or four meals uses the same total better than piling it into one. The meal to fix first is usually breakfast, which routinely lands at 10–15 grams; two eggs takes it to 30.

Quality: a gram is not a gram

The grams on a label are not identical to the amino acids that reach your tissues. Protein sources differ in digestibility and in amino acid profile, and the current measure for that difference is DIAAS: egg and dairy protein sit at the top, meat and fish just behind, while grains and legumes fall clearly further back, because wheat runs short on lysine and legumes on methionine.

The practical consequence is an addition, not a prohibition. Lentils and bulgur in the same meal cover each other’s gaps, and the resulting profile beats either one alone — which is what a great deal of traditional cooking has been doing for centuries. If you eat entirely plant-based, raising the daily target by roughly 10–20% is a reasonable correction.

The floor rises with age

Muscle responds more weakly to protein as you get older. The phenomenon is called anabolic resistance, and what it means in practice is that the 20 grams which trigger synthesis in a young body do not do the same job at sixty-five.

Expert groups (PROT-AGE, ESPEN) move the floor to 1.2–1.5 g/kg for adults over 65, and higher during illness or recovery — a week spent in bed costs muscle that takes months to rebuild, which makes protein most necessary exactly when appetite is lowest. The goal here is not performance. It is keeping the muscle that gets you out of a chair.

What it costs in calories

Protein carries 4 kcal per gram, so 140 grams is 560 kcal — around a quarter of a 2,000 kcal day.

The most durable order for building macros is to set protein first and split the remaining calories between carbohydrate and fat. The reason is simple: the protein target rests on a fixed rationale, while the other two are largely preference and tolerance. You can run the same 2,000 calories carb-heavy or fat-heavy and both will work. Drop the protein and the thing that stops working is the diet.

One detail gets overlooked here. Protein is expensive to digest — 20–30% of its calories are lost as heat, against 5–10% for carbohydrate and 0–3% for fat — so 560 kcal of protein contributes somewhat less than the label suggests.

Is more harmful?

In healthy people with normal kidney function, there is no evidence that high protein intake causes kidney damage. Athletic populations followed on high intakes for extended periods show no meaningful deterioration in kidney markers.

Existing kidney disease changes the picture entirely, and protein intake becomes something a doctor sets after looking at the stage of the disease and the person’s lab work rather than something a calculator suggests. None of the numbers in this article apply in that situation.

In practice the ceiling is set by budget and fullness rather than by safety. Raising the target takes room from the other macros, stops paying for itself past a point, and can fill the day so completely that people quit because it will not fit on the plate.

Working out your own number

The fastest route is entering your weight, goal and activity level and reading the range. The protein calculator below produces it; if you know your body fat percentage, the lean mass calculator narrows the answer considerably. Try hitting the number for a week before you change it, because most people’s protein problem is not the target on paper but the distance between that target and what actually reaches the plate.