Q&A: What to know about weight loss drugs

The biggest health and nutrition story of 2023 was arguably the exploding popularity of prescription medications to treat obesity, a chronic disease that affects more than four in 10 U.S. adults.

Health & Nutrition Letter spoke to Richard D. Siegel, co-director of the Diabetes and Lipid Center and a doctor at the Weight and Wellness Center at Tufts Medical Center and an associate professor at Tufts University School of Medicine, to get expert information and advice on weight loss drugs.

Health & Nutrition Letter: Two medications have become popular options for the treatment of obesity. What are these drugs?

Richard Siegel: Both Ozempic and Wegovy (which are made by the same manufacturer) contain the active ingredient semaglutide. Wegovy provides a higher dose. Both are delivered by self-injection.

Semaglutide mimics a naturally occurring hormone called GLP-1 that is released in the gut when we eat. GLP-1 prompts the body to produce more insulin and has actions in the appetite pathway in the brain. The doses of these medications are much higher than what the gut makes naturally. They seem to reduce cravings and dull the desire to eat.

In a trial published in 2021, adults with obesity taking semaglutide lost an average of almost 15 percent of their body weight in about one-and-a-half years. The placebo group lost an average of less than two-and-a-half percent. The only tool we have that leads to greater weight loss is bariatric surgery.

Are these drugs safe?

Ozempic has been used to treat type 2 diabetes since 2017, so we have a lot of data showing this class of drugs is safe, at least at lower doses.

The most common side effects are nausea and constipation. This is a result of the drug slowing down the digestive tract. There may be some risk for a condition called gastroparesis, which is slow stomach emptying, but this seems to be very rare. The package insert also mentions risk of gallbladder or kidney problems, pancreatitis, increased heart rate, and, in patients with type 2 diabetes, increased risk of low blood sugar and changes in vision.

A lot of people are taking Wegovy and Ozempic now. That means we are gathering a lot of additional real-world information about side effects and safety.

Do people taking these drugs need to make lifestyle changes, too?

The way I think of weight loss medications, in general, is as helpers to the lifestyle change approach. I recommend starting with self-monitoring, dietary changes, and increasing activity. If that is unsuccessful, we discuss adding "helpers" like surgery, meal replacement plans, and medication.

You can likely lose weight on semaglutide medications without changing your diet and activity behaviors, but these lifestyle changes will make the treatment more effective. Also, we don't know if weight loss will have the same health benefits if one does not change their behaviors.

Do you have to take it forever?

In one trial of Wegovy, people regained about two-thirds of the weight lost within a year of stopping the drug. Lifestyle changes can help maintain weight loss, but it's unusual to maintain all weight loss once you stop any weight loss medication.

Who should consider taking these drugs?

Wegovy is approved for use by adults and children aged 12 years and older with obesity and adults who are overweight and have weight-related medical problems like type 2 diabetes, high blood pressure, and/or sleep apnea. It is meant to be used in combination with calorie reduction and increased physical activity. Ozempic is not officially approved for weight loss, but many doctors prescribe it anyway. This is known as "off-label" prescribing and is perfectly legal.

I feel strongly that these medications should only be taken while working with a weight management team or a registered dietitian.

People looking to lose weight should meet with their primary care provider or specialists at a weight loss clinic and develop a personalized, comprehensive plan for weight loss and maintenance.