The Truth About Weight Loss Drugs

The so-called GLP-1-based therapies mimic hormones released by the small intestine when we eat, which help regulate blood sugar levels. They also trigger the production of insulin, a hormone that allows glucose to enter the body’s cells for energy. In addition, they slow digestion and enhance the feeling of fullness after eating.

For obesity, adults eligible for a prescription must have a body mass index of at least 30 or a BMI between 27 and 30, along with at least one weight-related health condition, such as type 2 diabetes, high cholesterol, or high blood pressure.

In a 2022 JAMA study, participants taking semaglutide lost 15.8 percent of their weight. Depending on the drug, it may also lower cardiovascular risk or the likelihood of kidney complications in those with type 2 diabetes, ease heart failure symptoms, reduce liver fat, improve metabolic dysfunction, and lessen the severity of sleep apnea. For example, A 2023 study in the New England Journal of Medicine found that semaglutide reduced the risk of death from heart disease and nonfatal heart attacks or strokes by about 20 percent for people who were obese or overweight. The weight loss can also lighten the load on hips and knees, and the drugs may help protect kidneys, too.

But people are likely to see a reversal of weight loss if they discontinue the drug. For instance, a study found that someone taking semaglutide who shed about 17 percent of their body weight could expect to regain about two-thirds of it after stopping the med. That suggests that when used for obesity, these drugs are intended for long-term use, even after people reach their target weight. "Some patients will end up on them for most of their lives, and that’s okay," says Christine Lovato, MD, a bariatric surgeon at Banner University Medical Center in Phoenix.

Some of these meds have been used to treat diabetes for over two decades and are generally considered safe. But more research is needed in populations such as older adults. Here are some of the potential side effects and possible risks.

• Gastrointestinal problems: Common side effects such as nausea, vomiting, and diarrhea may occur more frequently in older adults, according to John Batsis, MD, a geriatric obesity specialist at the University of North Carolina School of Medicine and Global Public Health in Chapel Hill. Eating frequent small meals may minimize the side effects. 

• Muscle loss: Semaglutide has been associated with the loss of lean body mass (muscle and bone), accounting for up to 40 percent of total weight loss. With these drugs, muscle mass may decline to the point where older adults are at risk for complications, such as falls.

• Nutrient deficiencies: Because the drugs suppress appetite and reduce caloric intake, some people may not get sufficient amounts of essential vitamins and minerals.

• Fracture: A 2026 study of adults with type 2 diabetes found that patients who started a GLP-1 faced an 11 percent higher risk of fractures than those taking other diabetes medications.

• Eye complications: The meds may carry a rare risk of eye-related side effects, such as a loss of blood flow to the optic nerve, which can cause permanent loss of vision.

If your doctor thinks that you could benefit from taking a GLP-1, follow these rules to prevent loss of muscle mass: Consume at least 30 grams of protein per meal, and do 15 to 20 minutes of resistance activities two or more times a week in addition to aerobic exercise such as brisk walking. Also, have your doctor monitor your nutrition status.