Decision 2 of 10

Why protein comes first

Protein is a target to reach, not a limit to stay under. The strongest reason is what your body keeps and loses while you are in a calorie deficit. The effect is smaller than most apps suggest.

Written and maintained by Mattias Geniar. Last updated .

What the app does
Shows protein as a target to reach, not a ceiling to stay under, and puts it above fat and carbohydrate on every screen.
How much we believe it
The effect on fat and muscle is well measured and under a kilogram. The claim that protein keeps you full is weaker than it is usually told, and after two years it disappears.

What this looks like in the app is on the protein first page. This page has the research behind it.

What more protein actually gets you

Wycherley et al. (2012) is the strongest evidence there is. It pooled 24 randomised trials with 1,063 people, all on diets with the same number of calories. Three of its four outcomes are in kilograms, so they can go on the same chart.

Higher protein against lower protein, at the same calories 24 randomised trials, 1,063 people, about twelve weeks. Point estimate and 95% confidence interval.
no difference
Body weight −0.79 kg

95% CI −1.50 to −0.08. Under one kilo of scale weight over about twelve weeks

Fat mass −0.87 kg

95% CI −1.26 to −0.48. More fat lost than total weight, which is the finding

Fat-free mass +0.43 kg

95% CI 0.09 to 0.78, kept rather than gained

−1.6 kg +1.0 kg
The fourth outcome is resting energy expenditure, which is in different units: +595.5 kJ/day preserved (95% CI 67.0, 1124.1), so it is not on this chart. The authors call the whole effect “modest”, and they are right. The gain is in what the lost weight is made of, not in how much is lost.

Their finding on fullness is weaker still: people felt fuller on higher protein in only 3 of the 5 studies that measured it.

Longland et al. (2016) is the best case anyone has shown: 40 young men, four weeks, 2.4 vs 1.2 g/kg/day of protein during a 40% calorie deficit, with all food provided and supervised training six days a week.

+1.2 kg lean mass, at 2.4 g/kg/day against +0.1 kg at 1.2 g/kg/day
−4.8 kg fat mass, at 2.4 g/kg/day against −3.5 kg at 1.2 g/kg/day
40 young men, four weeks, all food provided The authors call it a proof-of-principle trial

It does not predict what happens to somebody logging food on a phone. The supervision, the training six days a week, and the food handed over are exactly the things a phone cannot give you.

On fullness specifically

Kohanmoo et al. (2020) pooled 49 short-term and 19 long-term trials, all at matched calories.

How much less hungry, on a 100 mm scale Pooled across 49 short-term trials at matched calories. People mark how hungry they feel on a 100 mm line.
Hunger, how far it fell ≈7 mm

Out of the full 100 mm the scale runs to

Fullness, how far it rose ≈10 mm

The larger of the two, and still a tenth of the scale

0 100 mm, the whole scale
Real, clearly measured, and small. The long-term trials, 19 of them, found no effect on any measure of appetite.

The evidence against

After two years it makes no difference at all

POUNDS LOST (Sacks et al., NEJM 2009) assigned 811 adults to diets with 15% or 25% protein for two years: −3.0 kg vs −3.6 kg, p > 0.20. “Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets.” What did predict weight loss was turning up: 0.2 kg per group session attended.

Two years, 811 adults, and the thing that actually predicted the result Weight lost at 24 months, by the share of calories from protein.
15% protein −3.0 kg

Two years, 811 adults

25% protein −3.6 kg

p > 0.20 against the bar above. Neither bar is drawn in the page colour, because neither group won

0 5 kg lost
The gap is 0.6 kg and it is not statistically significant. Attendance was: 0.2 kg per session. Over the whole trial, that mattered far more than which diet somebody was assigned to.

Adding protein does not reduce what you eat

Ben-Harchache et al. (2021), 22 studies and 857 older adults: a protein drink before a meal cut that meal by 164 kJ. But once the drink's own energy was counted, total intake was higher by 649 kJ (95% CI 438, 861). Protein helps when it replaces other food at the same calories. Added on top, it does not.

Too little protein may matter more than extra protein

Gosby et al. (2011) found that cutting protein from 15% to 10% of calories made people eat 12% more. Raising it from 15% to 25% did not change how much they ate at all. That suggests the goal is to avoid too little protein, not to eat as much as possible. Martens et al. (2013) found the opposite. The two disagree, and that is the real state of the evidence.

And a caveat on our own number

The “about 30 g of protein per meal” rule in the recipe library comes from Schoenfeld & Aragon (2018), which recommends 0.4 g/kg per meal across at least four meals. That is a narrative review about muscle growth in people who lift weights. It is not a meta-analysis, and it is not about fullness or weight loss. Its lead author also declares an advisory role with a protein supplement company. We use it because a defensible minimum is better than no minimum, not because the question is settled.