A new report from Les Mills and ukactive urges stronger collaboration between the healthcare and fitness sectors to promote strength training and adequate protein intake as crucial interventions for people taking weight-loss drugs
When the World Health Organization updated its guidelines in favor of GLP-1 use to treat obesity, the global body made it clear that the weight-loss drugs shouldn’t be used in isolation, but in tandem with diet and exercise interventions.
A new global academic review put together by fitness company Les Mills and ukactive, the U.K.’s leading trade organization for the fitness sector, highlights that not only is exercise — especially strength training — important for those prescribed GLP-1s, but it is crucial to help maintain and prevent the loss of lean muscle mass.
As GLP-1 users rapidly lose weight, 20 to 50% of that could be lean body mass, according to the report. That’s because of the high caloric deficits, which lead to the body breaking down skeletal muscle tissue for energy.
“The loss of lean body mass (muscle and bone) associated with GLP-1 receptor agonists can have a significant negative impact on long-term health,” the report states.
Losing skeletal muscle mass can decrease resting metabolic rate, or how many calories your body burns at rest, for instance, making maintaining weight loss more difficult, especially when people come off of the drugs.
Uptake of the medication has surged in both the U.K. and the U.S. Nearly 2.5 million people reported to be using weight loss drugs in the U.K., with the British weight loss market experiencing an average monthly volume growth of nearly 25% between October 2024 and March 2025, while 12.4% of U.S. adults now say they’re using GLP-1 drugs like Ozempic and Wegovy for weight loss, up from 5.8% in early 2024.
With the scale and availability of fitness clubs, the authors point out there are ample opportunities for people taking medication to support the effectiveness of the medication and prevent muscle mass loss, with proper collaboration between sectors.
“Stronger integration between the healthcare and health and fitness industries is crucial to promote preventative care and empower these individuals to achieve their activity goals,” they wrote.
“The rapid rollout of GLP-1 has shown dramatic results for patients but in order to avoid weakening the body, there are simple and effective strength exercises which are essential for sustainable results,” said ukactive interim director of research, Dr. Matthew Wade.
“The health and fitness sector can support people taking weight loss medications, but we want to see the government go further by working with the fitness, nutrition and pharmaceutical industries to deliver the critical wraparound support patients need,” he added.
How to Maintain Muscle Mass While on GLP-1s
While the researchers point out that some muscle loss can be expected during a period of significant calorie deficit, typically high-dose GLP-1 or GLP-1/GIP receptor agonists are prescribed for initial weight loss, and then dosages are reduced for the weight maintenance phase. That’s where diet and exercise interventions come in.
General consensus on maintaining lean body mass (skeletal muscle and bone mass) while losing fat is through exercise, namely strength training, caloric restriction (which naturally occurs on GLP-1s) and adequate protein intake.
Based on current guidelines and research, the authors recommend resistance training two to three times per week at an intensity of 50 to 80% of one repetition maximum, with a minimum of seven exercises per session targeting large muscle groups.
More specifically, they recommend a progressive resistance training program starting with 10 to 15 repetitions of eight to 10 exercises twice per week, progressing to three sets of eight to 10 repetitions three times per week.
It’s not just resistance training that matters, though. The authors also encourage those on the medications to engage in 150 minutes of moderate to vigorous physical activity per week, to help continue fat mass loss in the maintenance phase of treatment.
Diet interventions are also essential, as the report indicates adequate protein intake helps preserve muscle mass accompanying rapid weight loss, while helping gain muscle during the weight maintenance period.
Ideally, those on GLP-1s should aim for 60 to 75 grams of protein per day, up to 1.5 grams per kilogram of body weight per day based on clinical guidelines, which also suggest small, nutrient-dense meals, including whole grains for satiety, sustained energy and reducing constipation.
It’s important to note that no randomised controlled studies have been performed yet on the effects of these recommendations, but rather they are based on clinical expertise.
“Regular strength training is vital to our health at all stages of life, but the research suggests this is especially true for people taking weight loss medications,” said Les Mills head of research Bryce Hastings.
“More research is needed to deeper understand the relationship between weight loss medications and strength training, but the evidence and recommendations in our report are the start of the journey and offer practical next steps to better support the growing number of people taking weight loss medication,” Hastings added.
Outside of working on this report, Les Mills has been pushing greater participation in strength training through its latest group fitness program, BodyPump Heavy, to encourage heavier weightlifting.
