GLP-1 medicines work. But the scale does not tell you which tissue you are losing. This free calculator estimates your daily protein target, your Muscle Protection Score, and the one or two changes that would move it most — whether you are on Ozempic, Wegovy, Mounjaro, or losing weight without medication.
GLP-1 receptor agonists such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) work largely by suppressing appetite. That is exactly why they are effective — and also why they create a nutritional problem that a bathroom scale cannot show you. When total intake falls, protein is usually the first thing to drop, because protein-rich foods are the most filling and the least appealing when you are already full.
The consequence is that weight comes off quickly, but not all of it is fat. Any rapid weight loss costs some lean tissue, and analyses of GLP-1 therapy have reported that a substantial share of the weight lost — frequently cited in the region of a quarter to 40% — can come from lean mass. Losing muscle lowers your resting metabolic rate, makes weight regain easier, and leaves you lighter but weaker.
Two levers reliably change that ratio: eating enough protein, and doing resistance training at least twice a week. Everything this calculator does is aimed at the first one, and it will tell you if the second is your weakest link.
The widely used reference intake of 0.8 g of protein per kg of body weight per day is a floor — the amount that prevents deficiency in a healthy, weight-stable adult. It was never intended for someone in a sustained calorie deficit. Guidance for preserving lean mass during weight loss sits considerably higher, commonly in the range of 1.2 to 1.6 g/kg per day, and higher still for older adults or anyone training seriously.
This tool starts from that per-kilogram logic and then adjusts for the things that actually change your requirement: your goal weight, your age, your activity level, and whether you do resistance training. One detail worth calling out — if your BMI is 30 or above, it doses protein on an adjusted body weight rather than your full scale weight, so you are not being prescribed protein to maintain excess fat mass.
Finally it compares that target against the protein you say you currently eat. The gap between those two numbers is the single most useful output on the page, and it is what the Muscle Protection Score is built from.
The protein requirement is driven by your body and your rate of loss, not by the specific molecule. What does differ between medicines is how strongly appetite is suppressed, which changes how hard hitting the target will feel in practice.
Both are semaglutide; Wegovy is dosed for weight management and Ozempic for type 2 diabetes. Appetite suppression tends to build as the dose steps up, so the protein gap often widens over the first few months even though nothing about your diet has consciously changed. Front-loading protein at breakfast, when appetite suppression is usually weakest, is the most practical fix.
Tirzepatide acts on both GIP and GLP-1 receptors and generally produces greater average weight loss. Faster loss means a larger absolute amount of tissue in play, so the share of lean mass you keep matters more, not less. If you are on a higher dose, treat your protein target as non-negotiable rather than aspirational.
Liraglutide (Victoza, Saxenda) and oral semaglutide (Rybelsus) follow the same principle with generally milder appetite effects. The calculator lets you pick your medicine and dose tier so the estimate reflects how suppressed your intake is likely to be.
With a suppressed appetite, the limiting factor is not willpower — it is volume. You need protein that is concentrated, so you hit the number before you feel full. Useful everyday anchors, using standard Indian household measures:
In practice most people on a GLP-1 can close roughly two thirds of the gap with food and struggle with the last third, simply because there is no room left. That is where a concentrated, low-volume source earns its place — a shake delivers 20 to 25 g in a few mouthfuls, which is far easier than another chicken breast when you are not hungry.
Most adults losing weight on semaglutide are guided toward roughly 1.2 to 1.6 g of protein per kg of body weight per day — well above the 0.8 g/kg baseline that only prevents deficiency. For an 80 kg adult that is about 96 to 128 g a day. Your exact number depends on your weight, goal weight, age, activity and how much you already eat, which is what the calculator above works out for you.
Yes. Any rapid weight loss costs some lean tissue, and studies of GLP-1 therapy have reported that a substantial share of the weight lost — frequently cited in the region of a quarter to 40% — can come from lean mass rather than fat. The two things that most reliably reduce that share are hitting your protein target and doing resistance training at least twice a week.
Under-eating protein while in a calorie deficit pushes your body to break down muscle for amino acids. In practice that tends to show up as fatigue, weakness, hair thinning, a slower resting metabolic rate and a body composition that looks softer at the same weight. Because appetite suppression makes it easy to fall short without noticing, tracking protein matters more on a GLP-1 than off it.
The calculator starts from your body weight and scales protein per kilogram, then adjusts for your goal weight, age, activity level and whether you do resistance training. If your BMI is 30 or above it doses protein on an adjusted body weight rather than your full scale weight, so you are not prescribed protein for excess fat mass. It then compares the target to what you say you currently eat to show the gap.
Yes. The calculator is completely free, needs no payment and runs in your browser. You enter your details, get your daily protein target and Muscle Protection Score, and can save or print the report.
If appetite suppression is the reason you cannot hit your target, GLP-1 Muscle Guard is built for exactly that situation — protein plus HMB in a low-volume serving, designed to protect lean mass while you lose weight.
Explore GLP-1 Muscle GuardThis calculator and the information on this page are for general educational purposes and are not medical advice, diagnosis or treatment. Protein requirements vary between individuals, and people with kidney disease, liver disease, or who are pregnant or breastfeeding should not change their protein intake without speaking to a doctor. Always consult your physician or dietitian about your own targets and before making changes to your diet or medication. Ozempic, Wegovy, Rybelsus, Victoza and Saxenda are trademarks of Novo Nordisk; Mounjaro and Zepbound are trademarks of Eli Lilly. Neither company is affiliated with Plant Genius or with this tool.
