How Do GLP-1 Agonists Cause Weight Loss?

Learn how GLP-1 agonists can help with weight loss. Discover how this medication can positively impact your metabolism, weight loss goals, & overall health.
Medical Reviewer: Elizabeth Lowden, MD
Published on: May 24, 2023
Updated on: November 2, 2023

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For many people, losing weight is hard. While lifestyle changes like following a healthy diet and engaging in regular exercise are important for weight loss, new medications are now available to help those for whom lifestyle changes alone are not enough to lose weight. FDA-approved weight loss medications include two GLP-1 agonist medications. Curious to find out about how GLP-1 agonists work in the body, and which GLP-1 agonist medication is best for weight loss? Read on to find out.

What Is a GLP-1 Agonist Medication for Weight Loss?

Glucagon-like peptide 1 (GLP-1) is a hormone that is naturally produced in the gut after eating. It stimulates insulin release, suppresses your appetite, and makes you feel fuller longer. GLP-1 agonist medications like semaglutide, which is sold under the brand name Wegovy®, mimic this hormone to help regulate blood sugar, cravings, and fullness. GLP-1 agonist medications were initially used to treat type 2 diabetes, but they have also been shown to be effective in weight loss.

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How GLP-1 Agonists Contribute to Weight Loss

GLP-1 agonists act in many tissues of the body, including the gut and brain, to help decrease hunger and thus food intake. This hormone works by slowing down the emptying of your stomach, so food stays in your stomach longer which leads to longer feelings of fullness. It also sends signals to the brain that the stomach is full which reduces the amount of food you eat. Additionally, GLP-1 agonists increase insulin release in response to eating and regulate blood sugar, which can reduce cravings for high-calorie foods. GLP-1 agonist medications mimic all of these mechanisms, which combined with lifestyle changes can lead to weight loss.

The use of FDA-approved weight loss medications such as GLP-1 agonists can be an appropriate weight loss tool when used along with lifestyle changes like healthy nutrition, increased physical activity, and mindset shifts. A healthcare provider can review your medical history to determine if a weight loss medication like a GLP-1 agonist is right for you as part of a comprehensive medical approach to weight loss.

Which GLP-1s Are Best for Weight Loss?

While there are several types of GLP-1 agonists used off-label for weight loss, there are currently only two GLP-1 agonists approved by the FDA for weight loss: Wegovy® (semaglutide) and Saxenda® (liraglutide). Both medications have been found to be effective in promoting weight loss when combined with a reduced calorie diet and increased physical activity.


Wegovy is a once-weekly GLP-1 agonist injectable that was approved by the FDA for weight loss in 2021. It contains semaglutide, the same active ingredient as Ozempic®, which is an FDA-approved medication for the treatment of type 2 diabetes, but is prescribed at a higher dose.


Saxenda is another GLP-1 agonist that was approved for weight loss in 2014. It is a once-daily injectable that contains the active ingredient liraglutide. Liraglutide is the same active ingredient in Victoza®, which is another FDA-approved medication to treat type 2 diabetes, but is prescribed at a higher dose for weight loss.

So which FDA-approved GLP-1 medication is best for weight loss? A 2022 study compared Wegovy 2.4 mg weekly to Saxenda 3 mg daily, the maximum doses of each medication used for weight loss, in adults with overweight or obesity without diabetes. At 68 weeks, the Wegovy group achieved an average weight loss of 15.8%, while the Saxenda group had an average weight loss of 6.4% when combined with dietary and lifestyle changes.

While these results are important to consider when choosing a treatment plan, there is not one weight loss medication that works for everyone. Weight loss results will vary from person to person and can be affected by many factors, including medical history, lifestyle, and preferences.

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Who Can Take GLP-1 Agonists for Weight Loss?

Wegovy and Saxenda are indicated for adults with obesity (BMI ≥30) or overweight (BMI ≥27) who also have weight-related medical conditions such as elevated blood pressure or high cholesterol. They are also approved for children 12 years of age and older with obesity. For the best weight loss outcome, GLP-1 agonists should be used in combination with healthy lifestyle changes.

Wegovy and Saxenda are available by prescription only and coverage will vary depending on your insurance carrier. It is important to check with your health insurance to determine coverage and understand any out-of-pocket expenses associated with these medications.

Like any medication, it is important to be aware of potential side effects. The most common side effects of Wegovy and Saxenda include nausea, diarrhea, vomiting, constipation, headache, and fatigue. Other less common but serious side effects include gallbladder problems, such as gallstones, acute kidney injury, and pancreatitis. There are also warnings on both medications about a rare thyroid cancer seen mainly in animal studies. Patients taking these medications should be monitored regularly by their healthcare provider.

The decision to start a medication should be reviewed with your healthcare provider. It is important to work with a medical weight loss program that understands your health history and goals in order to develop a treatment plan that is safe and works for you.

Alternatives to GLP-1 Agonists for Weight Loss

GLP-1 agonists are not appropriate for everyone. Wegovy and Saxenda should not be used if you have a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia syndrome type 2. GLP-1 agonists should also not be used if you are pregnant or trying to get pregnant or if you have had a serious allergic reaction to its ingredients.

For those looking for alternatives to GLP-1 agonists, there are other FDA-approved weight loss medications to consider such as Contrave (bupropion/naltrexone), Qsymia (phentermine/topiramate) and phentermine. For those who want to lose weight without medication, you can focus on lifestyle interventions such as eating a balanced diet, increasing physical activity, getting enough sleep, and working with a Registered Dietitian or other healthcare professional who specializes in weight management. The key is to find a sustainable plan that you can stick with for the long term.

GLP-1 Agonists Done the Right Way: How FORM Can Help

While there are several GLP-1 agonists suitable for weight loss, only Wegovy and Saxenda are FDA-approved for weight loss. FORM providers can prescribe these FDA-approved medications if medically appropriate. However, it is important to note that there are many reasons for not losing weight, and sometimes it is difficult to pinpoint the root cause. FORM can help individuals better understand their unique weight loss struggles and provide guidance on how to overcome them. Each patient is paired with a board-certified doctor and Registered Dietitian, who create a personalized and comprehensive plan based on their health history, current medications, and preferences. 

You can schedule a call or send a message to FORM to learn more, or take our quiz to find out if you are eligible.

Wegovy® is registered trademark of Novo Nordisk A/S.

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