GLP-1 Muscle Loss FAQ

GLP-1 medications lower your appetite. When you eat less, you often eat less protein too. When your body is short on calories, it breaks down some muscle along with fat. Eating enough protein and doing resistance training can tell your body to hold onto that muscle instead. Losing weight quickly can make muscle loss worse than losing weight slowly through diet alone.

Studies using DEXA scans suggest muscle can make up about 25 to 40% of the total weight lost on these medications if you don't take steps to protect it. For comparison, muscle usually makes up about 20 to 25% of weight lost through diet alone. Your own results depend on your age, your starting body composition, how much protein you eat, and how active you are.

Yes, you can protect a lot of it. The two things backed by the most evidence are eating enough protein and doing regular resistance training. Aim for about 1.6 grams of protein per kilogram of body weight each day. Aim for 2 to 3 resistance training sessions per week.

A common target is about 1.6 grams of protein per kilogram of body weight each day. That's higher than typical general guidelines, and it helps protect your muscle while you're eating less overall. If you train hard, some doctors and dietitians recommend as much as 2 to 2.2 grams per kilogram.

Yes. Lifting weights signals your body to build and keep muscle, even while you're losing weight. Studies on weight loss consistently show that people who strength train lose less muscle than people who only do cardio or don't exercise at all.

It's a score from 0 to 100. We build it from how often you do resistance training, how close your protein intake is to your target, and how fast you're losing weight. We layer that on top of published rates of muscle loss for people on GLP-1 medications. A higher score means your current habits are doing a better job protecting your muscle. Think of it as an educational estimate you can use to guide your choices.

Generally, yes. Losing weight faster tends to mean losing more muscle, no matter what method you use. Many doctors consider losing about 0.5 to 1% of your body weight per week a reasonable pace. If you're consistently losing weight faster than that, it may be worth talking to your prescriber about slowing down.

This is one of the most common worries people run into, and it makes sense why. The scale gets all the attention. Here's what's likely happening. If you're eating enough protein and doing resistance training, you might be losing fat and holding onto or even building muscle at the same time. Muscle is denser than fat, so your body can improve even while the number on the scale barely moves. Try tracking how your clothes fit or taking progress photos alongside the scale. Give it a few more weeks before assuming the medication has stopped working.

If you can get one, a DEXA scan is the most accurate way to track how your fat and muscle change over time. It gives you a much clearer picture than any calculator can. Think of this tool as something to use between scans, to help you understand your risk and stay on track.

Yes, and this doesn't get talked about enough. Rapid weight loss, including the weight loss from GLP-1 medications, can lower bone density along with muscle. This risk is higher for older adults and for women who have gone through menopause. The same things that protect your muscle also help protect your bones. Resistance training puts healthy stress on your bones. Enough protein and calcium give your body what it needs to maintain them. If you're in a higher risk group, it's worth asking your doctor whether a bone density scan makes sense for you.

We don't have much direct research comparing the two side by side yet. Mounjaro and Zepbound tend to produce more total weight loss on average. That can mean more total muscle lost overall, even if the share of muscle lost is similar. This calculator makes a small adjustment for that. Your own results will still depend on your habits.

It's completely normal to worry about this. Many people do gain some weight back after they stop a GLP-1 medication. If you lost muscle along the way and didn't do much to protect it, your metabolism may be a little weaker than before you started, which can make it easier to regain fat. The best time to protect yourself is now, while you're still on the medication. Keep your protein up and keep training so you carry as much muscle as possible into whatever comes next. Talk to your prescriber about a plan for stopping or tapering your dose when the time comes.

No. This tool gives you an educational estimate based on published research. Your prescriber or a registered dietitian knows your full medical history, labs, and body composition, and can give you advice suited to you. Talk with them before changing your medication, diet, or exercise routine.