You Need More Protein
On a Cut.

The number everyone knows is 1.6 grams of protein per kilo of bodyweight. It comes from a meta-analysis of 49 studies, and it's where the benefit of extra protein for muscle growth flattens out.^[1] It's a good number. It's also a number from people eating at maintenance or in a surplus, and it's the wrong number for a cut.

If you're building, you're probably eating more protein than you need. If you're cutting, you're probably not eating enough. Same nutrient, different job.

Why a deficit changes the maths

When you're eating enough, protein's job is to build. When you're not, protein's job is to stop the deficit being paid out of muscle. Those are different jobs and the second one needs more. A systematic review of protein intake during caloric restriction in lean, trained athletes found that the usual recommendations were too low, and that the people who held their muscle were eating 2.3 to 3.1 grams per kilo of lean mass a day.^[2]

The clearest trial is the one where it wasn't just preserved. Young men put in a 40% deficit for four weeks with hard training, on either 1.2 or 2.4 grams per kilo, lost similar fat. But the high-protein group gained 1.2 kg of lean mass and the low-protein group gained none.^[3] Same deficit, same training, double the protein, muscle built instead of held.

How much, then

On a cut, 2.2 to 3 grams per kilo of bodyweight, biased higher the leaner you are and the harder the deficit. An 80 kg lifter who gets by on 130 g in a surplus wants closer to 180 to 200 g in a cut. It sounds like a lot because it is. On a deficit it's also most of what you eat, which is fine, because protein is the one thing a cut can't do without.

Surplus: 1.6 to 2.2 g per kg. Cut: 2.2 to 3 g per kg. The leaner you are, the higher you go.

Per meal matters more when you're cutting

Protein synthesis per meal rises with dose until about 0.4 g per kilo, then flattens.^[4] At maintenance you can be sloppy about spreading it, because the day's total does most of the work. In a deficit the per-meal dose matters more: each meal is a chance to tip the balance toward keeping tissue, so three to five feeds at 0.4 to 0.5 g per kilo beats one big dinner.

What the app does

Coast sets your protein from your phase, not from a single number. In a build it sits at 1.6 to 2.2 g per kilo. In a cut it moves to the top of that range and above it, 2.2 to 3.1 g per kilo, spread across your meals at the per-meal floor. The meals in the library are built to carry that without turning every plate into chicken, which is the part most cutting diets get wrong.