Do Weight Loss Pills and Supplements Work? What NIH and FDA Say

Last updated October 27, 2026

Short answer: The NIH's National Center for Complementary and Integrative Health says the science does not support acai berry, bitter orange or green tea supplements for weight loss, and that none has been shown to produce meaningful weight loss in scientific studies. The FDA has also found weight loss products sold as supplements that contain hidden prescription drugs, and says it can lead to serious harm. Prescription medicines have far better evidence.

What NIH says about weight loss supplements

• The science does not support the use of acai berry, bitter orange or green tea supplements for weight loss, and none of them has been shown to produce meaningful weight loss in scientific studies.
• Most of these products have not been proven safe or effective, and the safety of many is uncertain. Many, including fat burners and appetite suppressants, have not been tested for safety.
• The FDA banned supplements containing ephedra in 2004, and replacement ingredients may cause similar side effects.
• Products with large amounts of caffeine or caffeine-containing herbs such as guarana may cause increased heart rate and abnormal heart rhythms.

What the FDA says about contaminated products

The FDA maintains a list of weight loss products found to contain hidden drugs. It says these products are sometimes falsely advertised as dietary supplements, food or all-natural treatments, that they pose a serious health risk and are not guaranteed to work, and that they can lead to severe health issues and hospitalization. It also says the list covers only a small fraction of the contaminated products on the market, and that a product not being on the list does not mean it is safe.

How to spot a risky product

• Claims like quick and effective or totally safe. NIH advises being wary of exaggerated claims.
• Testimonials. NIH points out that testimonials, anecdotes and opinions are not objective evidence.
• No ingredient list or an unfamiliar brand sold only online.
• A promise of results without diet or activity changes.

Capsules, patches and gummies

These are the same problem in different forms. Over-the-counter capsules, patches and gummies sold for weight loss are not the FDA-approved medicines. Read our guide on GLP-1 patches, gummies and drops for why the wording on these products can mislead.

What has stronger evidence

• FDA-approved prescription medicines, with results measured against placebo. See weight loss medications compared.
• Structured diet and activity programs, such as those tested in Look AHEAD and the Diabetes Prevention Program.
• Talking to a clinician before taking any supplement, which NIH recommends.

See weight loss medications compared, lifestyle vs. GLP-1 weight loss and is GLP-1 safe?