Peptides for weight loss: what you need to know

Peptides for weight loss are peptide-based medications that mimic hormones your body naturally produces to regulate appetite, digestion, and blood sugar. The most well-known options approved by the US Food and Drug Administration (FDA) — Wegovy, Zepbound, and Saxenda — may promote significant weight loss when paired with sustainable lifestyle changes to eating habits, exercise, and more.

Read on to learn more about peptide medications for weight loss, including how they work, which medications may be more effective, potential side effects, safety, and more. 

Peptides for weight loss are synthetic (manmade) peptide-based medications that mimic hormones the body naturally produces to regulate appetite, digestion, and blood sugar. FDA-approved peptides for weight loss include:

• Wegovy (semaglutide)

• Zepbound (tirzepatide)

• Saxenda (liraglutide)

See if you qualify

Peptide medications work for weight loss by mimicking GLP-1, a peptide hormone produced in the gut after eating. GLP-1 helps keep your blood sugar steady by increasing insulin and reducing. It also slows down digestion and reduces appetite by signaling to your brain that you’re full.  

Some peptide medications for weight loss, like Zepbound, also mimic a second gut hormone called glucose-dependent insulinotropic polypeptide, or GIP for short. GIP is also considered a peptide and works alongside GLP-1 to help keep appetite in check, improve insulin release, and help control blood sugar.

In mimicking these hormones, peptides for weight loss may work by:

• Increasing satiety. These peptide medications can help slow gastric emptying, or the rate at which food moves from the stomach to the small intestine. This can help you feel full sooner and stay satisfied longer after meals or snacks.

• Decreasing hunger cues. Peptide weight loss injections can activate GLP-1 receptors in the brain, helping to suppress appetite and quiet “food noise,” a nonmedical term that describes persistent, intrusive thoughts about food.

• Improving blood sugar control. These medications help the pancreas release more insulin when blood sugar rises, while also reducing glucagon, a hormone that raises blood sugar. Over time, weight loss from these medications can also help the body respond better to insulin.

Peptides that are FDA-approved for weight loss — such as Wegovy, Zepbound, and Saxenda — have gone through extensive testing for safety and efficacy. They are generally considered safe when used as directed by your prescribing healthcare provider. 

Due to an increased risk for certain side effects, these medications may not be suitable for everyone, including:

• People who are pregnant, breastfeeding, or planning to become pregnant

• People with a personal history of pancreatitis

• People with a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2 (MEN2). 

• People with a known allergy to any ingredients in the medication

If you’re interested in peptide medication, talk to a healthcare provider about getting a prescription for a weight loss medication. They can evaluate your health history and goals to determine if prescription peptide therapy is appropriate for you. 

Keep in mind that some retailers may sell “knockoff” versions of these medications or may market non-prescription peptide formulations that claim to promote weight loss. The FDA hasn’t vetted or approved these products, and they may come with health risks. 

Research suggests that semaglutide, liraglutide, and tirzepatide can all be effective tools for weight loss. In clinical trials, people lost approximately 8–13% of body weight with semaglutide, 5–8% with liraglutide, and 15–22% with tirzepatide when combined with changes to eating habits and exercise. 

That said, how much weight you lose with these medications depends on factors like your starting weight, lifestyle changes, underlying health conditions, the specific medication you’re taking, your dosage, and more. 

Let’s take a closer look at what the research says about the weight loss potential for each medication. 

Semaglutide (Wegovy, Ozempic) 

In a clinical trial, people with type 2 diabetes (who hadn’t previously received treatment aside from lifestyle changes) received 0.5 mg or 1 mg of semaglutide (Ozempic) as a once-weekly injection for 30 weeks (about 7.5 months). Participants taking 0.5 mg lost about 8 pounds on average. Those taking 1 mg lost an average of 10 pounds. These lower doses produced more modest weight loss than the higher 2.4 mg dose used in Wegovy, which is the FDA-approved formulation for weight management.

In another clinical trial, people with obesity or overweight without diabetes who took a once-weekly injection of 2.4 mg of semaglutide (the maximum dose of Wegovy) and followed a reduced-calorie diet and regular exercise lost an average of 15% of their weight in 68 weeks (a year and four months).

In a clinical trial of the daily Wegovy pill (25 mg), people lost 13.6% of their body weight in 64 weeks (about a year and three months).

Long-term studies also show promising weight loss outcomes. In the SELECT trial, semaglutide 2.4 mg was associated with an average weight loss of nearly 10% over two years in adults with overweight or obesity who also had heart disease. 

Liraglutide (Saxenda, Victoza)

A 2016 research review analyzing five liraglutide clinical trials found that the medication, along with changes to eating habits and lifestyle, produced weight loss of 5%–10% in most participants. 

People with and without prediabetes who completed a 56-week clinical trial and received 3 mg of liraglutide (the maximum dose of Saxenda) lost an average of 8% of their body weight in conjunction with lifestyle changes.

Tirzepatide (Zepbound, Mounjaro)

A 2022 clinical trial of people with obesity or overweight found that a once-weekly tirzepatide injection produced an average weight loss of 15%–21% in 72 weeks (a bit less than a year and a half). People who took the highest 15 mg dose of tirzepatide lost an average of about 21% of their body weight, or roughly 47 pounds. Notably, most of the participants on the 15 mg dose achieved at least 20% weight loss.

Benefits of prescription peptide medications for weight loss include:

• Significant weight loss (5%–20% in less than a year and a half)

• Steadier blood sugar levels

• Reduced food cravings

• Reduced waist circumference

• Less body fat, including belly fat (though some lean muscle mass loss may also occur)

• Lower blood pressure and cholesterol levels

• Reduced risk of other weight-related health conditions, such as heart disease

• Slowed progression of kidney disease in people with type 2 diabetes

• Improvement in obstructive sleep apnea and fatty liver disease (metabolic dysfunction-associated steatohepatitis, or MASH)

• May help improve symptoms of osteoarthritis

While GLP-1s and GLP-1/GIP medications are generally well tolerated, they can cause side effects, some of which can be serious.

Common side effects of weight loss peptides

The most common side effects of peptides for weight loss are mild, manageable gastrointestinal (GI) issues. Specific side effects can vary depending on which medication you’re taking but may include:

• Nausea

• Vomiting

• Abdominal pain

• Constipation

• Diarrhea

• Dyspepsia (indigestion)

To help mitigate the risk of side effects, your healthcare provider will likely start you on a low dose while your body gets acquainted with the medication before slowly increasing your dose to your maintenance level. Many of these side effects lessen with time as your body adjusts to the medication.

They may also recommend strategies such as eating smaller meals, avoiding certain foods and drinks, or taking anti-nausea medication to help manage mild GI side effects. 

Serious side effects of weight loss peptides

Serious side effects may also occur with GLP-1 medications, though they are rare and may include:

• Allergic reactions

• Inflammation of the pancreas (pancreatitis)

• Gallbladder problems

• Kidney problems

• Low blood sugar (hypoglycemia) in people with type 2 diabetes (especially when also using other medications that can lower blood sugar)

• Worsening of diabetic retinopathy (a condition that can cause blood vessel damage in the retina)in people with type 2 diabetes, particularly in those with pre-existing diabetic retinopathy 

• Gastroparesis (severe slowing of stomach emptying) or, even more rarely, bowel obstruction

• GLP-1 medications contain a black box warning about the potential increased risk for certain thyroid tumors. While this risk was only observed in rodent studies (not in humans), people with a  personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia type 2 (MEN2) syndrome should not take these medications.

There are currently three FDA-approved GLP-1 and dual GLP-1/GIP medications for weight loss.

Wegovy

Wegovy (semaglutide) is a GLP-1 receptor agonist that’s available as a daily pill or once-weekly injection. The single-use pen comes in five dose strengths: 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg. The pill comes in four dose strengths: 1.5 mg, 4 mg, 9 mg, and 25 mg. 

The Wegovy injection is FDA-approved for weight management in adults with obesity, in children aged 12 and older with obesity, or in adults with overweight who also have at least one weight-related health condition, such as dyslipidemia or high blood pressure. It’s also approved to treat certain types of fatty liver disease in adults. 

The Wegovy pill is FDA-approved for weight management in adults with obesity or with overweight and at least one weight-related health condition. Both the Wegovy pill and injection are also approved to help reduce the risk for major cardiovascular events (such as heart attack and stroke) in people with overweight or obesity who also have heart disease. 

Saxenda

Saxenda(liraglutide) is also a GLP-1 medication. Like the Wegovy injection, it’s approved for weight management in adults and children aged 12 and up who live with obesity and weigh more than 132 pounds, and for adults with overweight and a related condition, such as hypertension or high cholesterol. 

Saxenda is a daily injectable medication — it comes in a multi-dose pen that you inject once per day. Saxenda comes in 0.6 mg, 1.2 mg, 1.8 mg, 2.4 mg, and 3 mg doses. 

Zepbound

Zepbound (tirzepatide) is a dual-action GLP-1/GIP receptor agonist that mimics both GLP-1 and GIP hormones. It’s approved for weight loss in adults with obesity or adults with overweight who have at least one comorbid health condition. It’s also approved to treat moderate to severe obstructive sleep apnea (OSA) in adults with obesity. Zepbound is not approved in children.

Zepbound is a weekly injection available as single-dose pens, single-use vials, multi-dose vials, or a KwikPen that contains 4 doses. Zepbound comes in six dose strengths: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. 

Off-label peptides for weight loss

Other GLP-1 and GLP-1/GIP medications are approved for the treatment of type 2 diabetes rather than weight loss, but healthcare providers may sometimes prescribe these off-label to treat obesity or overweight. 

GLP-1 medications include Ozempic (semaglutide), Victoza (liraglutide), Trulicity (dulaglutide), and others, while GLP-1/GIP medications include Mounjaro (tirzepatide). 

GLP-1 and GLP-1/GIP medications work best when combined with sustainable lifestyle changes, such as:

• A balanced, nutritious eating plan

• Regular exercise, including both aerobic exercise and resistance training (about 150 minutes per week)

• Getting adequate sleep

• Managing stress

• Staying well hydrated

Think of these medications as just one part of your approach to weight management — lifestyle changes are just as important.

These medications are designed as long-term treatments, not quick fixes. Some people may take them indefinitely to maintain their results. Once you stop taking GLP-1 medications, you may experience a return of increased hunger and body weight. Healthy lifestyle changes — such as a balanced eating plan and regular exercise — may help with weight management.

If you’re interested in GLP-1 medications for weight loss, talk to your healthcare provider. They can help determine whether one of these drugs is appropriate for you or whether an alternative medication might better suit your health goals. 

Here are a few questions you may want to ask your healthcare provider about peptides for weight loss:

• Am I a candidate for weight loss treatment with GLP-1s or GLP-1/GIPs?

• Which peptide for weight loss is best for my health history and goals?

• What lifestyle changes should I make in conjunction with taking a peptide for weight loss?

• What should I do if I experience side effects?

• What can I expect long term?

• How much weight can I realistically expect to lose?

• How much do weight loss medications cost?

• Will my insurance cover my medication?

• Are there other alternatives I should try first?

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When used under the guidance of a knowledgeable healthcare provider, peptide therapy can be an effective tool for weight loss.  

• Peptides for weight loss include GLP-1 receptor agonist medications such as Wegovy and Saxenda, as well as dual GIP/GLP-1 receptor agonists like Zepbound. 

• These medications work by mimicking naturally occurring peptide hormones in the body that impact hunger, digestion, and blood sugar management. The combined effect of these actions can help promote weight loss. 

• Synthetic peptide medications can help promote significant weight loss, but they work best when paired with a balanced eating plan and regular exercise. 

• Weight loss peptides may cause GI side effects such as nausea, vomiting, diarrhea, and constipation. These common side effects are typically mild and manageable and tend to go away as your body adjusts to the medication. 

• Peptides for weight loss such as Wegovy, Saxenda, and Zepbound are FDA-approved medications that require a prescription from a licensed healthcare provider. Be wary of “knockoff” or non-prescription versions of these medications that have not been thoroughly tested for safety or efficacy.