Weight loss medications have changed what is realistic for people with obesity. Here is what the research shows, what you can reasonably expect, and what the trials do not tell us.
How do weight loss medications work?
The most widely used weight loss medications are GLP-1 receptor agonists, such as semaglutide. Tirzepatide acts on both the GLP-1 and GIP pathways. GLP-1 is a hormone your gut releases after eating. These medications mimic it, which reduces appetite, slows how quickly the stomach empties, and helps you feel full on less food. They also help the body release insulin when blood sugar rises.
How much weight can you lose?
Results depend on the medication, the dose, and how long you take it. The numbers below come from large clinical trials of FDA-approved products, where participants also received diet and activity counseling:
- Semaglutide (2.4 mg weekly): an average loss of 14.9% of body weight at 68 weeks, compared with 2.4% with placebo.
- Tirzepatide (5 mg to 15 mg weekly): an average loss of 15.0% to 20.9% at 72 weeks, compared with 3.1% with placebo.
- Head to head: in a 72-week trial comparing the two, tirzepatide produced an average loss of 20.2% versus 13.7% for semaglutide.
These are averages. Some people lose more, some lose less, and some do not respond well. Trial results for FDA-approved products may not apply to compounded medications, which are not tested in trials.
What is the weight loss timeline?
Doses are increased gradually over several months to limit side effects, so weight loss is steady rather than fast. In the trials above, participants kept losing weight for most of the first year or more. Expect to work with your provider on dose changes over time instead of seeing full results in the first month.
Do the benefits go beyond weight loss?
For some people, yes.
- Heart health. In a trial of more than 17,000 adults with overweight or obesity and existing cardiovascular disease, but without diabetes, semaglutide lowered the risk of heart attack, stroke, or cardiovascular death by 20% compared with placebo. This applies to people with established heart disease, not everyone.
- Blood sugar. These medications improve blood sugar control, and they were first developed for type 2 diabetes.
- Other conditions. Some FDA-approved products are now approved for related conditions, such as sleep apnea in adults with obesity. Your provider can tell you whether one applies to you.
- Brain health. The evidence is not established. Early interest in Alzheimer’s disease has not been confirmed in clinical trials, so this should not be a reason to start treatment.
What are the risks and side effects?
The most common side effects are nausea, vomiting, diarrhea, and constipation, usually worst when starting or raising a dose. More serious risks include pancreatitis, gallbladder problems, dehydration and kidney injury, and low blood sugar in people who also take insulin or certain diabetes medications. Semaglutide and tirzepatide carry a boxed warning for thyroid C-cell tumors, and should not be used by people with a personal or family history of medullary thyroid cancer or MEN 2. They are not recommended during pregnancy.
Some of the weight you lose can be muscle. Adequate protein and resistance training help protect it, and your provider can guide you.
What happens when you stop?
Most people regain much of the weight after stopping. In a follow-up of the semaglutide trial, participants regained about two thirds of their lost weight within a year of stopping. Obesity is a chronic condition, so ask your provider early about the long-term plan.
Who is a good candidate?
FDA-approved weight loss medications are intended for adults with obesity (BMI of 30 or higher) or overweight (BMI of 27 or higher) with a weight-related condition such as high blood pressure or type 2 diabetes. A provider decides based on your health history, your other medications, and your goals. They are not appropriate for everyone.
What to ask your provider
- Which medication is right for me, and why?
- What results are realistic for me, and over what timeframe?
- What side effects should I watch for, and when should I call?
- How will you monitor my progress and labs?
- What is the plan if I want to stop, or if I plateau?
DrWell and weight loss medications
DrWell providers evaluate each patient and prescribe only when it is medically appropriate. Some medications prescribed through DrWell are compounded, and compounded medications are not FDA approved. Your provider will explain which option is being prescribed and what that means for you.
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