Peptides for weight loss: results, medicines, and risks

How much weight did people lose?

One direct study compared the injections used in Zepbound and Wegovy for 72 weeks. Average weight loss was 20.2% with tirzepatide and 13.7% with semaglutide. These percentages describe the average change from starting body weight. They do not describe the amount every person will lose.

The study included adults with obesity, or overweight plus a related health problem, without type 2 diabetes. Both groups received lifestyle support and used the highest study amount they could tolerate. People and researchers knew which medicine was used. Eli Lilly, the tirzepatide maker, funded the study.

Stomach and bowel problems were the most common side effects in both groups. Results do not apply automatically to other medicines, pills, Wegovy HD, compounded products, or supplements. The study does not show which treatment suits one person.

Which medicines are approved for weight loss?

The labels state that Wegovy, Zepbound, and Saxenda are used with a reduced-calorie diet and more physical activity. Their products, patient groups, and safety risks differ.

Semaglutide is the active ingredient in Wegovy. The June 2026 label covers injection and tablet forms. Their labeled groups differ.

The injection is approved for long-term weight reduction in adults and patients aged 12 years and older with obesity. It is also approved for adults with overweight and a weight-related condition.

The tablets have weight-reduction uses for adults. The label also lists separate uses for heart and liver disease, each with its own limits. Do not present them as benefits for every person who wants to lose weight.

Zepbound is the weight-management product name for tirzepatide. Its April 2026 label covers long-term weight reduction for adults with obesity. It also covers adults with overweight and at least one weight-related condition.

Zepbound has a separate use for moderate to severe obstructive sleep apnea in adults with obesity. That use covers only adults with obesity and that condition.

Saxenda is the weight-management product name for liraglutide. Its February 2026 label covers adults and patients aged 12 years and older who weigh more than 60 kilograms and have obesity. It also covers adults with overweight and a weight-related condition.

FDA approved a first generic that refers to Saxenda in August 2025. That approval does not confirm pharmacy supply, coverage, or price.

Imcivree is setmelanotide. It activates the melanocortin-4 receptor, a protein that receives body signals. Its April 2026 label covers people aged 4 years and older with acquired hypothalamic obesity.

It also covers people aged 2 years and older with Bardet-Biedl syndrome. The label covers rare forms caused by changes in three genes: POMC, PCSK1, or LEPR. It does not cover common obesity or other types outside these conditions.

What risks and costs should you know about?

First ask whether the exact product has an approved weight-reduction use for the relevant group. Then check whether its form matches what is being offered. Check the current reasons not to use it, warnings, drug interactions, and follow-up needs.

An advertisement can show an average result with no product name or label. That leaves out the context needed to read the number.

Percentages from different trials do not create a fair ranking. Trials can differ in who joined, starting risk, lifestyle support, length, missing data, and treatment stopping. They can also measure different results. Direct comparisons are stronger, and they still apply only to the products, groups, and periods studied.

Safety warnings differ by product. The Wegovy, Zepbound, and Saxenda labels warn about a type of thyroid-cell tumor found in rodents. It is not known whether this applies to people.

The labels say not to use them with a personal or family history of medullary thyroid carcinoma, a type of cancer. They also name multiple endocrine neoplasia syndrome type 2, a rare inherited condition. The labels describe digestive-system side effects and other warnings.

Imcivree has different warnings because it is used in different people. These examples do not form a full safety review or injection guide. Read the current FDA label and patient guide for the exact product.

A quoted fee may leave out medicine, visits, tests, shipping, supplies, or follow-up. Check each service and the exact product before comparing totals. The sources reviewed here cannot confirm current price, coverage, or availability.

Still being studied: results in people without an approval.

Retatrutide is still being studied. It acts on receptors for three body signals: GIP, GLP-1, and glucagon. A receptor is a protein that receives a body signal.

A reviewed phase 2 trial enrolled 338 adults with obesity or overweight plus a related condition. The study followed treatment for 48 weeks.

The trial found more weight reduction at higher doses. It also found digestive-system side effects and heart-rate increases that rose with dose. The trial measured health results in people. FDA has not completed a review of benefits and risks, and no FDA-approved retail product exists.

ClinicalTrials.gov lists TRIUMPH-1, a late-stage phase 3 study, as completed. The record lists 2,335 participants and no summary results. An early summary from a sponsor cannot replace a complete peer-reviewed report, FDA review, or approved label. A planned submission does not guarantee approval or launch.

Cagrilintide is a long-acting version of the body signal amylin. A published mid-stage study tested cagrilintide alone. A later large study tested cagrilintide with semaglutide in adults with overweight or obesity.

These records show that cagrilintide has been studied in people. They do not make cagrilintide or the investigational combination called “CagriSema” FDA-approved.

FDA says retatrutide and cagrilintide cannot be used to make compounded drugs. Neither is a component of an FDA-approved drug. FDA has not found either one safe and effective for any condition. No record shows that an online product matches material used in a clinical trial.

Other fat-loss peptides have different evidence and limits.

AOD-9604 is often marketed as a fat-loss fragment of human growth hormone. FDA's 2024 review found that most studies did not show a weight-reduction benefit compared with placebo, an inactive comparison. One study enrolled 536 people with obesity and did not find significant weight loss.

The obesity development program ended after that failed study. Exposure in people does not by itself show a meaningful benefit.

CJC-1295 and ipamorelin are often sold alone or in blends with body-composition claims. Studies in people can show body changes, such as growth-hormone levels. These changes do not prove lasting fat loss, better function, or long-term benefits greater than risks.

FDA says that clinical data for CJC-1295 are limited. FDA also identifies serious unwanted events linked to it. For ipamorelin acetate, FDA raises concerns about immune reactions and whether its identity and contents were fully confirmed.

FDA cites serious events, including death, in a study where ipamorelin entered a vein to study stomach movement. That way into the body and study purpose do not show the risk for weight-loss injections. FDA says safety data for some other injection methods are absent.

MOTS-c is promoted with claims about metabolism and longer life. FDA says it has not found data from people who received drug products containing MOTS-c, for any way the product entered the body. Findings from body mechanisms, cells, or animals cannot establish weight loss in people. A substance record, patent, or clinic menu provides no health result and no FDA approval.

Do not put all these molecules in one “investigational” group. That word describes products still being studied. “Unapproved” describes FDA status.

Neither word shows how much evidence exists. Keep separate groups for controlled health results in people, body changes in people, and animal or cell findings. Failed programs and products with no reliable drug-product evidence in people need their own groups.

Is a product with the same ingredient the same medicine?

Not necessarily. A shared ingredient name does not prove the same benefits or risks. Products can differ in their other ingredients, strength, quality controls, and route into the body. A study result applies to the product tested, the people who took part, the comparison, the result measured, and the study length.

An FDA-approved medicine has a label that lists its approved uses and the groups of people those uses cover. An approved use is also called an indication. Check that label when a seller cites a study or says a product has “the same active ingredient.”

A compounded product is a separate product from the approved one.

Compounded medicines are specially prepared to meet a patient's needs. They are not FDA-approved.

Federal law has two main paths. Under section 503A, a pharmacy generally makes a compounded drug for one named patient. Under section 503B, an outsourcing facility can make batches if it meets legal rules. Neither path makes a compounded drug FDA-approved.

FDA does not review compounded drugs for safety, effectiveness, or quality before sale. Results from approved-product trials do not automatically apply. A prescription does not make a compounded drug an FDA-approved generic. Compounded and generic drugs follow different rules.

The difference drew attention during shortages, when consumers saw different vials, strengths, salt forms, and telehealth offers. FDA now states that semaglutide and tirzepatide do not appear on its drug-shortage list. FDA also reminds pharmacies and facilities that federal rules restrict copies of available drugs.

Limited cases can involve a documented clinical difference for one named patient. A marketing page cannot prove that a product qualifies.

FDA has received reports of unwanted events linked to compounded semaglutide and tirzepatide. One report does not prove that a product caused the event. As of May 31, 2026, FDA had received 990 reports linked to compounded semaglutide and more than 730 linked to compounded tirzepatide.

Many state-licensed pharmacies do not have to report these events to FDA. The total number of uses is unknown, so the reports give no dependable rate. Do not compare them directly with rates from approved-product trials.

Product problems include measuring errors, different strengths and containers, dose increases that do not follow the label, shipping-temperature complaints, and false labels. They also include semaglutide sodium or acetate. FDA says these salt forms are different active ingredients from the semaglutide in approved drugs.

FDA lacks information showing the same chemistry or effects in the body. A website's “same active ingredient” claim cannot resolve these differences.

Peptide supplements are a separate category.

A product labeled “peptides” and taken by mouth might contain collagen pieces, broken-down proteins, or other dietary ingredients. Such a product is a different thing from Wegovy, Zepbound, Saxenda, Imcivree, retatrutide, or another injected drug. The ingredients, how the body takes them in, product form, use, and evidence differ.

FDA does not approve dietary supplements for safety and effectiveness before sale. A claim such as “supports metabolism” does not show meaningful weight loss. FDA also warns that weight-loss products are often part of health fraud, and some have contained hidden drug ingredients. A product missing from a warning list has not been shown safe or effective.

When a supplement cites “peptide science,” the study should have tested that exact product and measured weight change in people. Evidence from an injection, a single protein, or a meal-replacement plan does not automatically apply. A similar word on the label does not establish a match.

What to check in a weight-loss offer

• What is the product called, what does it contain, and is it FDA-approved?
• Which current FDA label or original study supports the advertised benefit?
• Did the study test that benefit in the advertised group of people, and for how long?
• If the medicine is compounded, who makes it? Does the seller wrongly call it FDA-approved, generic, or equal to an approved medicine?
• If the product is still being studied or labeled for research, did the cited study test the product being sold?
• What does the ongoing price include? Which costs, insurance coverage, or supply details are still unknown?
• Will a licensed clinician assess the patient and answer safety questions about the exact product during follow-up?