Why protein should track lean mass, not bodyweight

Your protein target should be set per kilo of your fat-adjusted weight — your lean mass if you know your body-fat percentage, otherwise an estimate from your height — not your raw bodyweight. Extra body fat doesn’t need extra protein to maintain itself; only lean tissue does. Anchor the number there and it stays fair whether you’re carrying more fat or very little.

Most calorie trackers skip this distinction entirely. They multiply your scale weight by a flat protein factor and call it a target. That shortcut quietly breaks in both directions: it over-targets someone carrying more body fat, and under-targets a lean, muscular athlete who has less fat to begin with but more of the tissue that actually needs the protein.

Why doesn’t bodyweight work as the anchor?

Bodyweight is a mix of two very different tissues with very different protein needs. Muscle, organs, and other lean tissue are metabolically active and need a steady protein supply to maintain and repair. Fat mass is mostly storage — it doesn’t carry the same protein demand. When you set a target from total bodyweight, you’re implicitly asking fat mass to “earn” protein it doesn’t need, which inflates the number for anyone carrying more fat and leaves less room for everything else in the day — carbs, fat, the actual training fuel.

The fix isn’t complicated: use the weight of the tissue that matters. That’s lean mass if you can measure or estimate your body-fat percentage, or an ideal weight estimated from your height if you can’t. Either way, the anchor tracks the tissue doing the work, not the number on the scale.

How much protein does that actually mean?

There’s a well-established general range that sports nutrition guidance converges on for people training seriously: roughly the neighborhood of 1.6 to 2.2 grams per kilo of that fat-adjusted weight per day, trending toward the higher end when you’re in a calorie deficit and trying to hold onto muscle. That’s a general guidance range, not a precise number tied to your specific physiology — individual response varies, and the right number for you also depends on training type, session frequency, and how aggressive your calorie target is. Treat any specific figure as a sensible starting point, not a lab result.

The practical takeaway matters more than the decimal: if you’re cutting weight, your protein target should not be cutting alongside it. It should hold steady or climb, because you’re now asking your body to keep the muscle it has on fewer total calories.

Why does protein rise in a deep cut?

When you’re eating in a larger deficit, your body is short on total energy, and it will pull from whatever tissue is available to close the gap — including muscle, if protein and training don’t give it a reason not to. Raising the protein target as the deficit deepens is a defensive move: it signals to the body that muscle is not on the table, even while it’s drawing down fat stores.

This is also where the fat-adjusted anchor pays off twice. Someone cutting from a higher body-fat percentage has more fat to lose and can typically afford a more aggressive deficit — but their protein target, anchored to lean mass rather than total weight, doesn’t inflate just because the scale number is higher. They get an aggressive-enough cut without an inflated protein number that crowds out the rest of their macros.

What about fat, not just protein?

Fat follows the same logic as protein — it’s set per kilo of the same fat-adjusted weight, not raw bodyweight, for the same reason. Fat has real jobs (hormone production, nutrient absorption) that scale with lean tissue and general health needs, not with how much body fat you’re currently carrying. Once protein and fat are both set from the fat-adjusted anchor, whatever calories are left become carbs — the energy you actually earn from training, sized to the day you had.

How Sweatmeal does this

Sweatmeal sets your protein and fat targets per kilo of your fat-adjusted weight automatically — your lean mass if you’ve entered a body-fat percentage, otherwise an estimate from your height — and raises protein further as your deficit deepens in a cut. You never have to do the math or guess which number to anchor to; the app tells you when a figure is measured versus estimated, so you know exactly how much to trust it. The full breakdown of how every number is calculated, including calories and carbs, is on our methodology page.