Every protein calculator on the internet runs the same equation: take your body weight, multiply by a number between 1.2 and 2.0, and eat that many grams per day. At 85 kilograms (187 lbs), the math is manageable. At 120 kilograms (265 lbs), it spits out a target north of 190 grams — a number that would require protein at every meal, a shake between meals, and the quiet acceptance that your entire diet now revolves around hitting a quota your gut says can’t be right.
The problem is what the formula can’t see. It treats every kilogram the same — muscle, bone, organ, fat. A kilogram of quadricep and a kilogram of belly fat get equal billing. Protein requirements are driven almost entirely by fat-free mass — the tissue that actually uses amino acids to rebuild, contract, and maintain itself. Fat tissue doesn’t do any of that. It sits there, metabolically quiet on the protein front, while the calculator pretends it’s hungry.
Should You Calculate Protein from Lean Body Mass When Overweight?
Standard protein calculators overcount for overweight individuals because they treat fat mass the same as muscle. Nitrogen balance evidence converges on 1.85 grams per kilogram of lean body mass. A practical alternative: cap your body weight at BMI 30 and multiply by 1.2 g/kg. Both methods land on the same protein range — roughly half what per-total-body-weight formulas suggest.
— Weijs 2025 · Curr Opin Clin Nutr Metab Care · Nitrogen balance synthesis
A 2025 review by protein researcher Peter Weijs at Amsterdam UMC pulled together the nitrogen balance evidence and landed on a number: 1.85 grams per kilogram of lean body mass. That’s the threshold where nitrogen balance studies consistently converge — different populations, different methods, same destination.
For someone weighing 119 kilograms with about 61 kilograms of lean mass, the math changes dramatically. The per-total-body-weight approach would suggest somewhere around 190 grams per day. The lean-body-mass approach? About 113 grams. Not a rounding adjustment. A different weekly shop entirely.
The catch: most people don’t know their lean body mass, and DEXA scans aren’t exactly a Tuesday afternoon errand. Weijs offered a practical workaround. Cap your body weight at the equivalent of BMI 30, then multiply by 1.2 grams per kilogram. For the same 119-kilogram person at 1.65 meters tall, that adjusted weight comes out to about 82 kilograms — giving a target of roughly 98 grams per day. Two independent methods. Two calculations with nothing in common. Both landing in the same neighborhood.
That convergence is the part that matters. One pathway could be a researcher’s best guess. Two pathways arriving at the same protein range from opposite directions is harder to dismiss.
There’s an honest caveat worth sitting with. No trial has directly measured protein requirements in people with obesity as its primary question. The nitrogen balance data comes from pre- and post-bariatric surgery patients — an extreme population. And Weijs himself notes that someone who is obese but otherwise healthy and active might not need adjusted targets at all. The evidence is strong on direction but still building on precision.
What it does settle: the weight you’re trying to lose is the same weight inflating your protein target.
Every kilogram of fat your calculator counts is a kilogram that never asked for protein in the first place. Removing it from the equation doesn’t lower your standards. It corrects a formula that couldn’t tell the difference.
If you’ve been chasing a protein target that felt unreachable, the arithmetic was broken — not your discipline. The broader question of how much protein you actually need per day depends on more than weight alone, but for anyone carrying extra fat, the starting point just got a lot more honest.