Before beginning any new exercise program, consult your doctor. Stop immediately if you experience pain.
More than 15 million Americans are now losing weight with GLP-1 drugs. The medications — drugs like Ozempic, Wegovy and Mounjaro that were originally created to treat type 2 diabetes — have been shown to produce superior weight loss effects with little risk, according to a 2023 study.
If you’re taking one or considering it, though, it’s important to remember that using the drugs to suppress appetite doesn’t just contribute to fat loss. Taking them also can result in reduced muscle mass. How much is uncertain, but studies have indicated that anywhere between 15% to 60% of the weight people lose is lean muscle mass — meaning that if you shed 50 pounds, you will potentially be losing 7.5 to 30 pounds of your lean muscle.
“Many patients underestimate their weakness when on these drugs until it shows up functionally, like when they’re going up the stairs,” said Dr. Peter Wenger, an affiliate clinical assistant professor at Rutgers New Jersey Medical School. Wenger is also a family medicine and sports medicine physician in Lawrenceville, New Jersey, who regularly works with people on GLP-1s.
If you’re on a GLP-1 weight-loss program, it’s important to formulate a weekly exercise routine that includes strength training to protect your health and your physical independence. Strong muscles are key to maintaining sturdy bones and preventing falls, and they are important for long-term metabolic health.
Exercise and strength training to stave off too much muscle loss are especially critical if you’re 65 or older.
“People 65 and above are already at risk of sarcopenia,” said Dr. Viral Shah, an endocrinologist and director of diabetes clinical research at the Center for Diabetes and Metabolic Diseases at the Indiana University School of Medicine in Indianapolis. Sarcopenia is the age-related loss of muscle mass, strength and function. “If those people lose even 10% to 15% of lean mass, it’s still significant because they have low mass to begin with.”
But lost muscle mass isn’t good for anyone, no matter your age.
“Even when you’re relatively young, you feel so much older because you lose muscle mass so rapidly on these drugs,” Wenger said.
Wenger and other experts share tips on how to safely build muscle strength while using a GLP-1.
Before you rush to the gym and start pumping iron, be aware that while on a GLP-1, you may experience a reduced appetite and nausea, especially during the dose-adjustment phase at the start of your treatment. You may also feel fatigued and dizzy.
As a result, your strength training should begin with a lower intensity than the average person, and your progression to heavier weights should be more gradual.
“We recommend shorter sessions to accommodate nausea or fatigue,” Wenger said. “We also focus on complex dynamic movements like squats and dead lifts more than machines, as they teach coordination in using different body parts simultaneously.”
Ideally, a professional will develop an individualized exercise plan for you. If that’s not possible, Shah’s general recommendation to his GLP-1 patients is to do resistance exercises three times per week and aerobic exercise another three days.
Regular movement is definitely important, said Stan Ward, senior personal training manager at fitness club Equinox, who is based in Plano, Texas.
“Movement can be very productive for your energy levels, even if it’s low-level movement like walking or biking,” Ward said. “And make sure you’re getting adequate sleep. That’s commonly overlooked.”
Experts emphasize the importance of taking in enough protein every day, which is key to building muscle. Specifically, Shah said people on GLP-1s need about 1 to 1.2 grams per kilogram of weight. For someone weighing 150 pounds (68 kilograms), that equals 68 to 81.6 grams of protein daily.
The timing of your protein intake, along with the necessary carbohydrates, is also important.
“Because people on GLP-1s have reduced appetites and sometimes nausea, that can lead to underfueling,” Wenger said. “They will often not eat for extended periods of time. But if you don’t plan your meals around your workouts, that can contribute to even more muscle loss.”
This is because your body needs nutrients both to fuel your workouts and, afterward, to replenish your energy stores and repair muscle tissue.
Wenger recommends eating an hour or two before exercising since GLP-1s slow digestion.
“Eating too close to a workout may lead to bloating, nausea and cramping,” Wenger said, “particularly with moderate to high-intensity training.”
Liquid snacks such as smoothies are best, he said, as they’re better tolerated than solid food.
After your workout, refuel within 30 to 60 minutes, which is when your muscles will be ready to take in nutrients.
“If your appetite is low, a protein shake or small snack with protein and carbs, such as Greek yogurt with fruit or chocolate milk, can be more manageable than a full meal,” Wenger said.
All this planning may sound like a lot of work, but there is good news, Ward said.
“It can be hard to see you need to put some thought into this, when the medication is doing all of the work,” Ward said. “But those who never used to exercise, or exercise regularly, can really see significant gains in their bodies.”
Since the use of GLP-1s for weight loss is a new practice, more studies will be needed to determine how to best help the people using them, Shah said, especially when it comes to specific recommendations for exercise, nutrition and the building of lean muscle mass.
“We do not have good data to say ‘X’ type of exercise or amount is going to give the best results,” Shah said.
Until then, make sure to incorporate strength training into your weekly exercise regimen — even if you’re not on a GLP-1.
“Studies have shown your longevity and quality of life are all tied to muscle,” Ward said. “And if you increase your muscle mass, you’ll burn more calories, even at rest. So improving your muscle mass should be part of any training program. If I could find a way to shout this from the mountaintops, I’d love it.”
Melanie Radzicki McManus is a freelance writer who specializes in hiking, travel and fitness.
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