Protein, leucine & muscle — straight answers

Leucine is the amino acid that flips on muscle protein synthesis through the mTOR pathway. Hit about 2.5-3 g of leucine in a meal and your body starts building.

The leucine threshold is about 2.5 g per meal for younger adults and closer to 3 g for older adults, the dose that maximally switches on muscle protein synthesis.

Sedentary adults need about 0.8 g of protein per kg of body weight; for building or keeping muscle aim higher, around 1.6 g per kg (roughly 0.7 g per pound).

Aim for about 20-40 g of quality protein per meal, enough to clear the ~2.5-3 g leucine threshold that maximally triggers muscle growth.

Constant hunger, slow recovery, stalled muscle, hair thinning, weak nails and getting sick often can all point to too little protein.

Chicken breast, Greek yogurt, eggs, lean beef, fish, lentils and tofu pack the most protein per bite. Here are the real numbers.

Eggs, canned tuna, lentils, dried beans, oats, milk and peanut butter give the most protein per dollar, no supplements needed.

A medium cooked chicken breast (about 170 g) has roughly 50 g of protein, well over the leucine threshold for one meal.

One large egg has about 6 g of protein, so it takes roughly 3-4 eggs to reach the leucine threshold for a meal.

While dieting, push protein to about 1.8-2.2 g per kg of body weight to stay full and protect muscle, spread as 25-30 g per meal.

Greek yogurt, cottage cheese, a tuna pouch, edamame and a scoop of whey are the most filling protein-per-calorie snacks for losing fat.

Lean on soy (tofu, tempeh, edamame), beans, lentils, dairy and eggs, eat a bit more total protein, and combine sources across the day to cover all the amino acids.