GLP-1 Protein Calculator for Zepbound & Wegovy

Which body weight goes into the g/kg?

Every protein calculator has to pick a basis, and almost none of them tell you which one they picked. The 2025 joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society is unusually candid about it: it says outright that "it's unclear whether these goals should be based on actual body weight, corrected (adjusted or ideal) body weight, or fat-free mass", and then lands on adjusted body weight — 1.2 to 2.0 g/kg of adjusted body weight per day — for people in major weight reduction.

Here is what that choice is worth, for one person:

That last row is deliberate. The guidance says to use adjusted body weight and does not say how to calculate it, so any calculator that hands you an adjusted-weight number is using an equation it chose itself. Half of that arithmetic is at least standard — the ideal body weight calculator (Devine, Robinson, Miller, Hamwi) gives you the ideal-weight half — but the correction factor on top of it is not something the advisory supplies.

Two guardrails sit either side of all of this, and they are the other thing nobody on this topic publishes: protein intake in adults should not fall below 0.4–0.5 g/kg/day, and prolonged intake above 2 g/kg/day should be avoided. A target without a ceiling is only half an answer.

How much protein do you need on a GLP-1?

The research ranges look contradictory until you sort them by goal. The UK/BDA general baseline is about 0.75 g/kg — but that's for a healthy adult who isn't in a calorie deficit. During active weight loss on semaglutide or tirzepatide, the joint advisory lands at 1.2–1.6 g/kg, and if you're also lifting to hold onto muscle, 1.4–2.0 g/kg — the range the International Society of Sports Nutrition gives as sufficient for most exercising individuals. The longer-form version of this, with the food examples, is how much protein on Ozempic, Wegovy and Mounjaro explained.

The reason is simple: when you lose weight fast, a chunk of what you lose can be lean mass unless protein and resistance training defend it. On a GLP-1 your appetite is doing you a favor on calories and working against you on protein — so protein stops being a budget to stay under and becomes a floor to clear.

How much protein do people on a GLP-1 actually eat?

Rarely enough. A 2025 cross-sectional study of 60 adults who had been using a GLP-1 receptor agonist for at least a month found mean intakes of 88.1 ± 30.1 g/day in men and 74.4 ± 28.6 g/day in women. Measured against adjusted body weight, only 43% met even 1.2 g/kg/day; 10% met 1.6 g/kg/day and 5% met 2.0 g/kg/day. It is a small study (n = 60), cross-sectional, and published in a journal supplement — not a trial — but it is the only direct look at the question.

The shape of the failure matters more than the headline. Almost nobody is aiming too low. What happens is that the floor gets missed on the days appetite is worst — dose-increase weeks, nausea days, the week a new vial starts — and those days are invisible unless something is counting. That is the entire argument for tracking rather than estimating.

Why the per-meal split matters

Total daily protein is only half the story. The ISSN position stand puts the per-meal dose at 0.25 g of high-quality protein per kg of body weight, or an absolute 20–40 g, and says those doses "should ideally be evenly distributed, every 3–4 h, across the day". Note that the per-meal figure scales with body size too — it is not simply the daily total divided by the number of meals. For resistance-trained people in a hypocaloric period, the same position stand notes that 2.3–3.1 g/kg/day may be needed to maximise retention of lean mass.

The joint advisory's practical overlay fits neatly on top: eat breakfast and then small meals every 3–4 hours while drinking adequate fluids, and put the protein-rich food first in the meal "to increase the likelihood of sufficient consumption". When appetite crashes on dose-increase weeks, front-load protein earlier in the day while you still have room. Pushing protein up without moving fibre and fluid with it is how the constipation starts, so pair this with your daily fibre target on a GLP-1 and how much water to drink on a GLP-1. For worked per-meal examples, see how many grams of protein per meal on Ozempic.

Zepbound, Mounjaro, Wegovy, Ozempic: does the protein target change?

No. The target follows your body weight, your goal and your training — not the molecule. What does differ between the two drugs is how much of the weight lost is lean mass. In the STEP 1 DXA sub-study about 40% of the weight lost on semaglutide was lean, against roughly 26% on tirzepatide in the SURMOUNT-1 DXA sub-study. But STEP 1's placebo group also lost about 25% of its weight as lean mass, which tells you this is largely a property of fast weight loss rather than of the drug. The joint advisory frames the same STEP 1 result in kilograms: of an average 13.6 kg reduction, 8.3 kg (62%) was fat and 5.3 kg (38%) was lean body mass.

The full comparison is in Zepbound vs Wegovy muscle loss: what the DXA data shows, and for UK readers, where tirzepatide is Mounjaro for both indications, Mounjaro vs Ozempic muscle loss (UK). Either way the advisory's answer is the same for both molecules: pair the medication with a structured exercise programme — strength training at least 3 times weekly, plus at least 150 minutes of moderate-intensity aerobic exercise a week.

Turning the number into a habit

A calculator gives you a target once. The Tiro app turns it into a tracked daily floor with a running per-meal bar, so you can see the gap and close it before bed — and it reminds you to lift protein higher exactly when your dose steps up and intake dips. Chronically under-eating protein while losing weight fast has downstream costs that show up weeks later, including the protein connection behind Mounjaro hair loss.