GLP-1 Protein Calculator

GLP-1 medicines, such as semaglutide and tirzepatide, lower appetite, so many people eat much less, including less protein. When weight comes off, part of it is lean mass, not only fat. A GLP-1 protein target is the grams of protein a day that experts suggest to help keep that lean mass while you eat less.

What This Protein Target Measures

The result is a daily intake goal, not a measure of your muscle. It depends on your body size, not on which GLP-1 medicine you take, and it gives no advice about medicines or doses.

The Formula

Daily protein (g) = 1.2 to 1.6 x reference weight (kg)

Reference weight = your current weight, if your BMI is under 30

Reference weight = adjusted body weight, if your BMI is 30 or more: ideal body weight + 0.4 x (current weight - ideal body weight)

Ideal body weight (Devine): 50 kg for men or 45.5 kg for women, plus 2.3 kg for each inch over 5 feet

The 1.2 to 1.6 g/kg range comes from a 2025 joint advisory by four US medical, nutrition and obesity groups, which also warns that using full body weight can overstate protein needs in people with obesity¹. The adjusted weight step uses the same formula as our Adjusted Body Weight Calculator.

How This Calculator Computes Your Result

Enter your sex, age, height, weight, whether you strength train, and whether you eat 3 or 4 meals a day. The calculator converts pounds and feet to metric, finds your BMI, picks your reference weight, and multiplies it by 1.2 and 1.6. Your suggested target is 1.6 g/kg if you strength train, or 1.4 g/kg (the middle) if you do not, split evenly across your meals. With a BMI of 30 or more, you also see the range on your full weight. Optional boxes show your range at a goal weight, and a lean mass check at 1.5 g per kg of lean mass if you know your body fat percentage¹. Grams are rounded to the nearest whole gram.

What Your Result Means

Here is how your range compares with the protein levels in the joint advisory¹:

For example, a 165 cm (5 ft 5 in) woman weighing 105 kg (231 lb) has a BMI of 38.6 and an adjusted body weight of 76.1 kg. Her range is 91 to 122 g a day, and without strength training her target is 107 g, about 36 g at each of 3 meals. On her full weight it would be 126 to 168 g.

A 2024 expert review for people on weight-loss medicines suggests more than 60 to 75 g a day during weight loss⁶. If your range starts below 60 g, the result points this out.

Why Lean Mass Matters on a GLP-1 Medicine

In a body scan (DXA) substudy of the STEP 1 semaglutide trial, 5.3 kg of the 13.6 kg of fat and lean tissue lost (38%) was lean mass¹. In the SURMOUNT-1 tirzepatide trial, lean mass fell 10.9% on the medicine and 2.6% on placebo². Across 7 placebo-controlled trials that measured lean mass, about 30% of weight lost was lean mass². Muscle makes up about half of lean mass, so roughly 20% of weight lost may be muscle¹. Trial designs differ, so these numbers are not a fair way to compare medicines.

Protein helps. Across 24 trials of reduced-calorie diets, higher-protein diets kept 0.43 kg more lean mass than standard-protein diets³. But the advisory says protein alone is likely not enough and suggests strength training at least 3 times a week¹. In 49 studies of 1,863 healthy adults who strength trained, extra protein added to lean mass gains up to about 1.6 g/kg a day, with no clear extra gain above that⁴. That is why the target moves to 1.6 g/kg if you strength train.

Older age raises the risk of muscle loss¹. An ESPEN expert group advises at least 1.0 to 1.2 g/kg a day for healthy older adults, and this range sits at or above that⁷.

How to Spread Protein Across Your Meals

Spreading protein evenly may help your muscles use it. In a small study of 8 adults, about 30 g of protein at each of 3 meals led to 25% more muscle protein building over 24 hours than eating most of it at dinner⁵. With a small appetite, eating the protein part of a meal first can help¹. Good sources include beans, peas, lentils, dairy, seafood, eggs and lean poultry¹, and meal replacement products with 15 to 25 g of protein per serving can fill gaps⁶.