How much protein for weight loss?

The short answer

Somewhere between 1.6 and 2.4 g of protein per kilogram of body weight per day. For a 75 kg person, that's 120–180 g.

Where you sit in that range depends on two things: how lean you already are, and how aggressive your deficit is. Both push you higher. Someone at 30% body fat losing weight slowly can sit near the bottom. A lean person cutting hard for an event belongs at the top.

Why the number goes up when you eat less

This is the part that catches people out. Most nutrition advice scales with how much you're eating — if you eat less, you get less of everything. Protein is the exception, and it moves the other way.

When you're in a calorie deficit, your body needs energy it isn't getting from food, so it breaks down stored tissue to cover the gap. Some of that is fat. Some of it is muscle. Your body doesn't especially care which, and it will happily take both.

Eating more protein, combined with resistance training, shifts that ratio substantially towards fat. That's the entire mechanism. Protein isn't burning anything — it's changing the composition of what you lose.

What the evidence actually shows

The clearest demonstration is a 2016 trial by Longland and colleagues. Young men were put into a steep 40% calorie deficit for four weeks, trained hard six days a week, and were given either 1.2 g/kg or 2.4 g/kg of protein.

Both groups lost roughly the same amount of fat. The difference was what happened to lean mass: the high-protein group gained about 1.2 kg of it, while the lower-protein group essentially held steady. Under a severe deficit, that's a striking result.

The study is worth reading in context — it used young trained men, an extreme deficit and a very high training volume, so the exact numbers don't transfer cleanly to everyone. But the direction is consistent across the literature, and the practical lesson is robust: when calories are low, protein is what stands between you and losing muscle.

The satiety effect, honestly measured

Protein is the most filling of the three macronutrients, calorie for calorie. This matters more than it sounds, because the hardest part of any diet isn't the arithmetic — it's still wanting to eat at nine in the evening.

A meal built around a substantial protein source keeps you fuller longer than the same calories from carbohydrate or fat. That doesn't make the deficit disappear, but it makes it survivable, and adherence is the only variable that reliably predicts whether a diet works.

You'll also see the thermic effect of food cited: roughly 20–30% of the energy in protein is spent digesting it, against 5–10% for carbohydrate and 0–3% for fat. This is real. It is also small. Swapping 50 g of carbohydrate for 50 g of protein buys you something in the region of 30 calories a day. Worth knowing; not worth planning around.

If you have a lot of weight to lose

Protein requirements track lean mass rather than total mass, and body fat is metabolically cheap to maintain. So for someone at 140 kg, multiplying by 2.0 g/kg gives 280 g a day — a target that's difficult to eat, expensive, and higher than the evidence supports.

Two better approaches:

• Use your goal weight. If you're 140 kg aiming for 95 kg, calculate from 95. It's crude but it lands far closer than the raw number.
• Use an adjusted body weight. Take the weight you'd be at a BMI of 25, then add a quarter of the excess. This is the correction our protein calculator applies automatically when you enter your height.

Either way, the resulting target will be meaningfully lower and considerably more achievable — and achievable is the whole point.

Where the protein should come from

In a deficit, every calorie has to justify itself, which makes protein density the thing to optimise. The useful question isn't "how much protein is in this?" but "how much protein per calorie?"

• Excellent: chicken breast, turkey, white fish, prawns, egg whites, fat-free Greek yoghurt, low-fat cottage cheese, whey protein, tofu, seitan.
• Good but calorie-dense: salmon, whole eggs, lean beef, full-fat dairy, tempeh. Nothing wrong with these — they just cost more of your budget per gram of protein.
• Not the protein source you think it is: peanut butter, most nuts, most protein bars. Nuts are a fat source that happens to contain protein.

None of this makes any food off-limits. It's about where the bulk of your protein comes from, not policing every meal.

A workable plan

1. Set a target from the range above, rounded to something memorable. 140 g, not 137 g.
2. Track for two weeks without changing anything else. You need to know your actual starting point, and almost nobody guesses it correctly. Most people are 30–50 g lower than they assume.
3. Anchor each meal. Decide the protein source first and build the rest of the plate around it. This is a far more reliable habit than trying to catch up at dinner.
4. Keep training. Protein protects muscle in a deficit largely because resistance training gives the body a reason to keep it. Protein without training does much less.

The gap between a 150 g target and a 155 g target is noise. The gap between your target and what you're actually eating is the whole story — and you can't close a gap you haven't measured.

Common questions

Where these numbers come from

The ranges here draw on the International Society of Sports Nutrition position stand on protein and exercise; Helms and colleagues' 2014 review in the International Journal of Sport Nutrition and Exercise Metabolism, which is the source of the higher figures for lean dieting athletes; Longland and colleagues' 2016 trial in the American Journal of Clinical Nutrition, which compared high and low protein intakes under a steep deficit with training; and Leidy and colleagues' 2015 review of protein and satiety. The thermic effect figures come from standard nutrition texts and are consistent across sources.