GLP-1 Medication Exercise and Nutrition: Protecting Muscle on Ozempic and Mounjaro
In the trial that won semaglutide its weight-management approval, the participants who had body-composition scans lost around 8.4kg (18lb) of fat and 5.3kg (12lb) of lean mass (Wilding et al., NEJM, 2021). Close to two-fifths of what came off the scale wasn't fat. If your sport depends on your legs, back and grip, that second number is the one to watch.
On GLP-1 medications such as semaglutide or tirzepatide, appetite drops and muscle can be lost alongside fat. Protecting it takes protein of roughly 1.2–1.6g/kg of bodyweight daily, prioritised at every meal, and resistance training on at least two, ideally three, days a week. Active users should plan training fuel with their prescribing doctor.
Disclaimer: This post is education, not medical advice. It doesn't cover starting, stopping, changing or sourcing any medication; those decisions belong to the doctor who prescribed it.
Quick overview
What is GLP-1 exercise nutrition trying to protect?
Muscle, and the training capacity built on it. GLP-1 medicines slow stomach emptying and turn appetite down, so people taking them often eat far less without deciding to. When intake drops that sharply, the body draws on lean tissue as well as fat.
How much depends on the drug and the trial. In STEP 1, lean mass made up about 38% of the weight lost on semaglutide. In SURMOUNT-1, about a quarter of the weight lost on tirzepatide was lean mass, the same split seen in the placebo group, who lost weight through lifestyle changes alone (Look et al., Diabetes Obes Metab, 2025).
Two caveats keep those figures honest. Scan-measured lean mass includes water, organs and connective tissue, so it isn't all muscle; a 2025 joint advisory from four US obesity and nutrition bodies models actual muscle loss at around 10–15% of weight lost in women and 20–25% in men who don't strength train (Mozaffarian et al., Am J Clin Nutr, 2025). And some lean loss comes with any large weight loss, diet alone included, and whether it harms function is still argued (Conte et al., JAMA, 2024).
For someone who trains, I don't wait for that argument to settle. Strength per kilo, bone loading and how well you tolerate a training week all rest on keeping muscle.
How much protein do you need on a GLP-1 medication?
Around 1.2–1.6g per kilo of bodyweight a day is the most widely cited target, and a sensible figure to open the conversation with your doctor. Where that number comes from is worth knowing. The joint advisory lists 1.2–1.6g/kg as a target proposed during active weight reduction in general, with 80–120g a day as a simpler absolute alternative (Mozaffarian et al., Am J Clin Nutr, 2025). It wasn't derived from trials in people taking GLP-1 drugs. A 2026 commentary notes there are no prospective studies establishing the right amount on these medicines, and that current advice is largely borrowed from bariatric surgery (Spreckley et al., Int J Obes, 2026).
At 80kg (176lb), 1.2–1.6g/kg is 96–128g of protein a day. Spread across four eating occasions, that's roughly 25–30g each time.
If you're carrying a lot of weight, a doctor or dietitian may calculate the target from an adjusted bodyweight rather than scale weight, which brings it down to something you can actually eat. That's their call, and one reason not to set this number alone.
For context, the general range for trained athletes is 1.2–2.0g/kg (Thomas et al., J Acad Nutr Diet, 2016). The GLP-1 figure sits inside it, but athlete guidance doesn't transfer automatically to someone on medication.
How do you eat enough protein when you're not hungry?
Eat the protein first, in smaller portions, more often. With slower stomach emptying, a large plate becomes hard work a few bites in, so protein should be what's eaten before fullness arrives.
A 250ml (about 8.5fl oz) glass of milk gives around 8g of protein, 150g (5oz) of Greek yoghurt or hung curd about 15g, 100g (3.5oz) of paneer or firm tofu around 15–18g, and two eggs about 12g. A bowl of dal, a tin of tuna, a chicken breast or a piece of fish gets a meal most of the way.
Soft and liquid foods often go down more easily on low-appetite days: lassi, kefir, a smoothie made with milk or soy milk, dal soup, congee with an egg stirred through, cottage cheese on toast. If a protein shake is the only thing that goes down on a rough day, it's food like any other, but check with your doctor or dietitian that it suits you.
Appetite drugs can blunt thirst too, and nausea makes it easy to drink less. Sip through the day and drink deliberately around training, more in heat and humidity.
Why resistance training matters as much as the protein
Protein without a loading stimulus protects far less muscle, which is why the joint advisory pairs its protein guidance with structured strength training and regular aerobic activity (Mozaffarian et al., Am J Clin Nutr, 2025). Trial evidence on combining exercise with these drugs is still thin. In one Danish trial, people who paired an older GLP-1 medicine with regular exercise kept their lost weight off better than those using either one alone, and lost about twice as much body fat (Lundgren et al., NEJM, 2021).
In practice, that's two or three full-body sessions a week built on a squat or leg press, a hinge, a push, a pull and a carry, with loads that progress over time. Runners, cyclists and footballers should keep the lifting even when the main sport feels like the priority. If you're returning from injury, set the programme with a physiotherapist.
Can you fuel hard training on a suppressed appetite?
Yes, with planning, and this is where people who train hard on these drugs most often come unstuck. Low appetite plus high training volume is a direct route to low energy availability and, over time, Relative Energy Deficiency in Sport (REDs) (Mountjoy et al., Br J Sports Med, 2023). The signs are flat sessions, poor sleep, frequent colds, stalled strength and, in women, disrupted periods.
Put carbohydrate before and after your hardest sessions, in forms that are easy to eat: a banana, toast with honey, a few dates, rice, poha or a bagel. For how much you need, see how many carbs athletes need; for changing body weight without losing performance, see losing weight as an athlete.
Some situations need your doctor involved before you train hard. If you also take insulin or a sulfonylurea, low blood sugar during exercise is a real risk. Vomiting or diarrhoea before long or hot sessions raises the risk of dehydration. If you compete under anti-doping rules, check your medication's status and any exemption process with your national anti-doping organisation.
These are prescription medicines for specific medical conditions. Nothing here is a case for using them to make weight, change physique or improve performance.
The Fueletics Perspective
If you train on one of these medicines, protein at every meal and two or three lifting sessions a week, decide whether you end up smaller and weaker or leaner and still capable. Judge progress by three or four lifts and how your hardest sessions feel, not by the scale alone.
Take your real training week to your prescribing doctor: sessions, duration, and intensity. Ask what protein target they want and which bodyweight it's based on, whether a dietitian referral makes sense, and how they'd like to monitor muscle. Mention side effects that land on training days and every other medication you take.
Fueletics works on food and training. It doesn't manage, adjust or support a prescription; your doctor stays in charge of that. Training-day and rest-day protein and carbohydrate depend on your schedule, your body and your sport, and no blog range can set them. If you want those numbers worked out from your actual week to take to your doctor, start with a Fueletics assessment.
FAQ
Should you exercise while taking Ozempic or Mounjaro?
For most people, yes, especially resistance training. Clinical guidance pairs GLP-1 treatment with strength training and aerobic activity to protect muscle. Agree the plan with your prescribing doctor.
How much protein should I eat on a GLP-1?
Roughly 1.2–1.6g/kg of bodyweight a day, or 80–120g a day, is the commonly cited target. Evidence in GLP-1 users specifically is limited, so set yours with your doctor or a dietitian.
Does Ozempic cause muscle loss?
Some lean mass is lost alongside fat, as with most large weight losses. Adequate protein and regular resistance training are the best-supported ways to limit it.
What should I eat before a workout on a GLP-1?
Something small, low in fat and fibre, and carbohydrate-based, eaten early enough that it doesn't sit heavily. There's more in what to eat before a morning workout.
Research References
Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384(11):989–1002. doi:10.1056/NEJMoa2032183
Look M, Dunn JP, Kushner RF, et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight. Diabetes Obes Metab. 2025;27(5):2720–2729. doi:10.1111/dom.16275
Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Am J Clin Nutr. 2025;122(1):344–367. doi:10.1016/j.ajcnut.2025.04.023
Conte C, Hall KD, Klein S. Is weight loss–induced muscle mass loss clinically relevant? JAMA. 2024;332(1):9–10. doi:10.1001/jama.2024.6586
Spreckley M, Ruggiero CF, Brown A. Bridging the nutrition guidance gap for GLP-1 receptor agonist therapy assisted weight loss: lessons from bariatric surgery. Int J Obes. 2026;50:265–267. doi:10.1038/s41366-025-01952-w
Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3):501–528. doi:10.1016/j.jand.2015.12.006
Lundgren JR, Janus C, Jensen SBK, et al. Healthy weight loss maintenance with exercise, liraglutide, or both combined. N Engl J Med. 2021;384(18):1719–1730. doi:10.1056/NEJMoa2028198
Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073–1097. doi:10.1136/bjsports-2023-106994
