Should You Base Your Protein Target on Current Weight or Goal Weight on a GLP-1?

A 2025 joint advisory from four obesity and nutrition societies quietly flagged a problem with the protein math most people use. Targets of 1.2 to 1.6 grams per kilogram have been proposed during active weight loss, but for people with obesity the authors write that it is unclear whether that kilogram should be actual weight, adjusted or ideal weight, or fat-free mass, because using actual weight can significantly overestimate protein needs (see [1]). Run it for someone who weighs 120 kilograms and the range lands at 144 to 192 grams a day. The same paper notes GLP-1 medications cut calorie intake by 16 to 39 percent. That is a lot of chicken for a shrunken appetite.

The method the advisory calls more accurate is about 1.5 grams per kilogram of lean body mass, which needs body composition data. If that 120-kilogram person carries roughly 60 kilograms of lean mass, the target drops to about 90 grams. Without a scan, the authors offer a plainer fallback: an absolute 80 to 120 grams a day, or 16 to 24 percent of calories on a 2,000-calorie diet, partly because a number people can hit is a number they keep hitting (see [1]). They also caution against holding intake at or above 2 grams per kilogram for long stretches. The kitchen tip in the advisory is the one I would underline: put the protein-rich part of the plate first, since a reduced appetite often quits halfway through a meal (see [1]). Greek yogurt, eggs, lentils, a piece of salmon.

Why bother getting it right? In the STEP 1 semaglutide trial, 38 percent of the average 13.6 kilograms lost was lean mass, which the advisory estimates works out to roughly a fifth of the weight lost being muscle (see [1]). A small study presented at ENDO 2025 followed 23 adults on semaglutide for three months and found that, after accounting for how much weight they lost, being older, being female, and eating less protein were each linked to losing more lean mass (see [2]). It was observational and tiny, so it shows an association, not proof that more protein prevents the loss. For how daily targets get set in the first place, our protein intake guide walks through the ranges.

This is general information, not medical advice — talk to a qualified clinician about your own situation.