The downside to taking Ozempic: Why GLP-1 drug users are freaking out about this one side effect

Ozempic and other GLP-1 drugs have exploded in popularity as dramatic, seemingly effortless weight-loss stories flood social media feeds. Celebrities have acknowledged using them, with tennis legend Serena Wiliams becoming a spokeswoman for Ro, a health care firm selling GLP-1 drugs. What’s more, people with type 2 diabetes have seen striking improvements in blood sugar, and the drugs’ ability to curb appetite has made them one of the most talked-about medical products of the past two years. But alongside the enthusiasm, a quieter concern has emerged among doctors and patients: the same mechanism that helps people shed significant weight can also cause them to lose something they desperately want to keep. Increasingly, users are discovering that GLP-1 drugs may take a noticeable toll on muscle mass.

The startling benefits of Ozempic

Ozempic, the brand name for semaglutide, is a once-weekly injectable medication belonging to a class known as GLP-1 receptor agonists. In the United States, it is approved for improving blood sugar control in adults with type 2 diabetes and for reducing cardiovascular risk in patients who already have heart disease. A higher-dose version of the same molecule is sold under the name Wegovy, which is specifically approved for chronic weight management. Although these drugs were not originally designed as weight-loss treatments, one of their most significant effects is how profoundly they can reduce appetite. By mimicking a hormone involved in satiety, semaglutide slows digestion, moderates the liver’s release of glucose and signals to the brain that the body has had enough to eat. For many people, that combination leads to a substantial drop in daily calorie intake and steady weight loss without the constant battle against hunger.

A huge change to the weight loss landscape, but it’s not all good news

That effect has made GLP-1 drugs enormously popular among people seeking to lose weight. Clinical trials of semaglutide at the doses used for obesity treatment have shown average weight reductions of around 15 percent over a little more than a year. That level of weight loss can have major health benefits for people with obesity and conditions linked to excess weight. But the surge in demand has also created risks. Patients are cautioned to obtain these medications only through licensed clinicians, to avoid counterfeit or grey-market versions and to be wary of compounded formulations that may not meet regulatory standards.

The growing concern relates to what kind of weight is lost. Any significant weight reduction, whether achieved through strict dieting, bariatric surgery or GLP-1 therapy, leads to loss of both fat and lean tissue. Lean tissue includes not only muscle but organs and other fat-free mass. The worry among clinicians is that the appetite-suppressing effects of these drugs are so strong that many users inadvertently consume too little protein and perform little or no strength training. That combination creates ideal conditions for losing muscle at a faster rate than expected.

Studies examining GLP-1 drug users show that while most of the weight they lose is fat, a meaningful portion comes from lean mass, often around a quarter or more of total weight lost. Some analyses suggest that a range of roughly 20 to 40 percent of lost weight may be lean tissue, depending on the patient’s age, sex, starting health, lifestyle and the dose of the medication. This pattern is particularly concerning for older adults, who already face age-related muscle decline and a higher risk of frailty. Many patients also describe a subjective sense of weakness or reduced physical capacity, despite seeing promising numbers on the scale.

Losing muscle doesn’t mean just losing strength

The consequences of excessive muscle loss extend beyond strength. Muscle plays a major role in maintaining metabolic rate, meaning that losing too much lean mass can slow the metabolism and make long-term weight maintenance harder. Lower muscle mass can also increase the risk of falls and injuries, reduce functional independence in older age and contribute to a phenomenon known as sarcopenic obesity, in which someone may weigh less but still have an unhealthy balance of fat and muscle.

Doctors emphasise that muscle loss is not inevitable and can be mitigated with the right approach. Resistance training is considered the most effective intervention for preserving muscle during weight loss, as it stimulates the body to maintain and rebuild the tissue even when calories are reduced. This does not require heavy lifting or gym memberships; structured body-weight exercises, resistance bands or machine-based training can all play a role when performed consistently.

Diet and strength training

Adequate protein intake is equally important. Because GLP-1 drugs suppress appetite so strongly, many users unintentionally fail to meet basic protein requirements. Including a meaningful protein source at each meal, spreading intake throughout the day and using protein supplements when needed can help protect lean mass. Clinicians also caution against letting the medication drive patients into extreme calorie deficits, which only increases the likelihood of losing muscle and can worsen fatigue and other side effects.

Doctors increasingly advise monitoring not just weight but strength, energy levels and, when possible, changes in body composition. For older patients or those already experiencing muscle weakness, closer supervision is especially important.

Ozempic and similar medications remain highly effective treatments for the conditions they were designed to address, and they can be transformative for many people struggling with obesity and metabolic disease. But the enthusiasm surrounding their weight-loss effects should be balanced with a clear understanding of what that weight represents. These drugs can help people lose fat, but without careful attention to exercise, nutrition and medical guidance, they can also take more muscle than intended.

This article is for general information only. It is not medical advice and should not replace consultation with a qualified health professional. Always speak with your doctor before starting or adjusting any medication or making significant changes to your diet or exercise routine.

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