GLP-1 Agonists for Weight Loss: Do They Work?

By Irmanie Hemphill, MD, FAAFP
Medically reviewed checkmarkMedically reviewed
January 17, 2023

Key takeaways

  • GLP-1 agonists mimic a hormone in your body that helps slow gastric emptying, increase insulin secretions, and decrease sugar production in the liver.

  • Wegovy and Saxenda are the only GLP-1 agonists approved for weight loss in people with a BMI of 30 or greater or with a BMI of 27 or greater who also have weight-related medical conditions.

  • The most common side effects include nausea, vomiting, constipation, and diarrhea.

GLP-1 agonists are a special kind of medication, originally designed to help people with type 2 diabetes control their blood sugar. However, these injectable medications also proved to assist with weight loss during clinical trials.

Currently, Wegovy and Saxenda are the only FDA-approved GLP-1 agonists approved for weight loss in those without diabetes. However, users must meet specific criteria. Other GLP-1 agonists are approved for use in people with type 2 diabetes, but not for weight loss alone.

Read on to learn more about GLP-1 agonists, how they work, their risks, and more.

What Are GLP-1 Agonists?

GLP-1 is a hormone that helps regulate blood sugar levels. It does this by: 

  • Decreasing the amount of glucose the liver releases
  • Increasing the amount of insulin the pancreas releases
  • Slowing gastric emptying
  • Increasing feelings of fullness

GLP-1 agonists are medications that behave similarly to the GLP-1 hormone. These medications come in liquid form and are given as subcutaneous injections. Each drug has several potential side effects. The most common include nausea, vomiting, and diarrhea.

During clinical trials, participants who used a GLP-1 agonist while following a limited-calorie diet and increasing physical activity had more significant weight loss than participants who did not.

The United States has currently approved four GLP-1 agonist medications. Several key differences exist between the medications, including their dosing, administration, tolerability, and patient satisfaction. Before choosing which GLP-1 agonist is right for you, consider your options and discuss them with your medical provider. 

Wegovy

Wegovy (semaglutide) is a once-weekly injection for adults with a BMI of 30 or greater—or a BMI of 27 or greater with weight-related medical problems. The medication works best when combined with a reduced-calorie meal plan and increased physical activity.

During a 68-week medical study, adults lost an average of 38 pounds (lbs) or 15% of their starting body weight while taking Wegovy and following the diet and exercise guidelines. 

Trulicity 

Trulicity (dulaglutide) is a once-weekly injection for adults with type 2 diabetes. During studies, Trulicity helped 50%–67% of participating adults lower their A1C to below 7% after four doses. And while the makers of Trulicity are clear this is not a weight loss drug, some study participants lost up to ten pounds.

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Victoza

Victoza (liraglutide) is a once-daily injection for adults and children over ten years of age with type 2 diabetes. It promotes lower blood sugar levels and A1C. It also helps decrease the risk of major cardiovascular events such as stroke and heart attack. During clinical trials, many adults with type 2 diabetes lost an average of 6.2 pounds. However, some adults gained weight.

Ozempic

Ozempic (semaglutide) is another once-weekly injection for adults with type 2 diabetes. It assists in lowering blood sugar levels and A1C when taken with a reduced-calorie diet and increased physical activity.

Although not considered a weight loss drug, taking Ozempic with a reduced calorie diet and increased physical activity may help promote weight loss. It may also reduce the risk for cardiovascular events such as heart attack and stroke in people with type 2 diabetes and heart disease. In clinical trials, adult participants lost up to 14 lbs.  

Saxenda

Saxenda (liraglutide) is a once-daily injection for adults with a BMI of 30 or greater, adults with weight-related medical problems, and children aged 12–17 years with a body weight above 132 pounds and obesity.

Users should increase physical activity and follow a reduced-calorie diet. During testing, 85% of participants lost weight while taking Saxenda. About half of the people who experienced weight loss maintained the loss one year after taking Saxenda. 

Byetta

Byetta (exenatide) is a twice-daily injection typically taken before morning and evening meals. The medication helps control blood sugar in those with diabetes. As with other GLP-1 agonists, it’s essential for users to increase physical activity and reduce calorie intake when taking Byetta.

Other GLP-1 Agonists

Several other GLP-1 agonists are also available in the U.S. and Europe. 

  • Bydureon (exenatide): available in the U.S. as a weekly injection
  • Lyxumia (lixisenatide): available in Europe as a daily injection
  • Tanzeum (albiglutide): available in the U.S. as a weekly injection 
  • Eperzan (albiglutide): available in Europe as a weekly injection

Pros and Cons

When used properly, these medications can be highly beneficial, potentially providing improved glucose control and decreased risk of complications associated with diabetes and obesity.

Other benefits include:

  • Reduced cardiovascular risks
  • Possible once-a-week therapy
  • Increased patient satisfaction

However, there are several risks associated with using GLP-1 agonists. While some people enjoy the ease of a once-a-week injection, others may find an injection uncomfortable or difficult. The most common side effect associated with GLP-1 agonists is stomach discomfort, nausea, and diarrhea or constipation.

Other cons include:

  • Increased risk of developing pancreatitis
  • Possible increased risk for thyroid cancer
  • Potential side effects
  • Cost of the medication
  • Injection site reactions 

Ultimately, people considering a GLP-1 agonist should weigh the pros and cons to determine if the medication is the best option. Understanding the risks and benefits of each medication can help you make an informed decision. It’s essential to talk with your healthcare provider about any questions or concerns that you may have.

Who Are They For?

GLP-1 agonists were originally intended for adults with type 2 diabetes. However, several are now available as weight loss medications for people who don’t have type 2 diabetes—including Wegovy and Saxenda.

Several qualifications must be met for a healthcare provider to prescribe one of these medications for weight loss. These include:

  • BMI of 30 or greater
  • BMI of 27 or greater with a weight-related medical condition
  • Children aged 12–17 with a body weight of 132 lbs or above with obesity (Saxenda)

People who desire to use a GLP-1 agonist must also realize these medications are designed to work alongside increased physical activity and a reduced-calorie meal plan.

Do not take GLP-1 agonists if you ever have an endocrine system condition called Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) or if you or a family member have had medullary thyroid carcinoma (MTC). It’s important to note that these medications have not undergone testing in people with kidney, liver, or pancreatic conditions.

How Do GLP-1 Agonists Work?

GLP-1 agonist work in three ways:

  • Slow gastric emptying: When food leaves your stomach slower, it helps control your blood sugar after meals and promotes fullness.
  • Prevents your liver from making extra sugar: Your liver releases glucagon throughout the day, which can raise your blood sugar level.
  • Helps your pancreas produce more insulin when your blood sugar is high: Insulin tells your cells to absorb sugar which helps lower your blood sugar level.  

It’s important to note that GLP-1 agonists do not work for everyone, and combining them with other medications, such as metformin or insulin, may be necessary.

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Side Effects and Risks

Although these medications have many benefits, they also have potential side effects. The most common side effects include:

  • Constipation or diarrhea
  • Nausea
  • Vomiting
  • Stomach pain
  • Heartburn or indigestion
  • Bloating, belching, and flatulence
  • Headache
  • Fatigue
  • Dizziness
  • Low blood sugar in people with type 2 diabetes

Side effects that are less common but more severe include:

  • Allergic reaction
  • Pancreatitis
  • Gallstones
  • Kidney injury
  • Changes in heart rate
  • Suicidal behavior or ideation
  • Risk of thyroid tumors
  • Diabetic retinopathy in people with type 2 diabetes

Alternatives

Medications aren’t always the best solution for weight loss, and many people may be able to reduce their weight by making lifestyle changes. The following strategies may help you lose weight:

  • Increase fiber and protein intake: Adding more fiber and protein to your diet curbs appetite and promotes fullness.
  • Avoid processed foods: Processed foods typically contain saturated and trans fats, excess sugars, and sodium.
  • Reduce sugar intake: Eating too much sugar can lead to weight gain and increase your risk of type 2 diabetes—or worsen existing diabetes.
  • Increase physical activity: Regular exercise helps burn calories and fat and can lead to long-term weight loss.
  • Get adequate sleep: Not getting enough sleep can cause an increase in appetite and increase cortisol which can increase weight gain, leading to weight gain.
  • Talk to a registered dietitian: Working with a registered dietician can help you lose and maintain weight.
  • Get regular check-ups: Regular check-ups from your medical provider will help you stay informed about your health and can help you prevent or identify any potential medical problems.

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Frequently Asked Questions

Which GLP-1 agonist works best for weight loss?
Currently, the only two GLP-1 agonists approved for weight loss include Wegovy and Saxenda. The other GLP-1 agonists are only approved for people with type 2 diabetes. However, medical providers sometimes prescribe other GLP-1 agonists off-label for weight loss.
Do GLP-1 agonists help you lose weight?
Yes, taking a GLP-1 can help some people achieve their weight loss goals.
How do GLP-1 agonists cause weight loss?
GLP-1 medications help promote feeling full for longer by slowing gastric emptying. They also tell your pancreas to release more insulin and your liver to slow glucose production, which helps keep blood sugar balanced.
Do you need a prescription for GLP-1 agonists?
Yes, GLP-1 medications require a prescription from a licensed medical provider. They are only approved under specific qualifications, such as having type 2 diabetes, a BMI of 30 or greater, or a BMI of 27 with other weight-related medical conditions.

K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Irmanie Hemphill, MD, FAAFP

Dr. Hemphill is an award winning primary care physician with an MD from Florida State University College of Medicine. She completed her residency at Halifax Medical Center.

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