Weight-loss supplements rated by evidence: what pooled trials show for fiber, berberine, green tea, creatine and more, plus FDA hidden-drug warnings and interactions.
Fact-checked against FDA labels and official sources; not yet reviewed by a licensed clinician. This page is education, not medical advice. Talk to your doctor before starting, stopping or changing any treatment.
Key takeaways
- By statute the FDA does not approve dietary supplements for safety or effectiveness; no supplement is FDA approved for weight loss.[1]
- Pooled trials show most weight-loss supplements add little or nothing: green tea -0.04 kg outside Japan, glucomannan -0.22 kg (not significant), garcinia -0.88 kg.[12]
- The FDA has found weight-loss products hiding sibutramine, diuretics, antidepressants and other drugs.[4]
- NCCIH says acai, bitter orange and green tea have not been shown to produce meaningful weight loss, and many weight-loss supplements were never tested for safety.[2]
- Berberine, green tea and fiber supplements can change how prescription medicines work; check with a pharmacist first.[8]
In short: No dietary supplement is FDA approved for weight loss; by law the FDA does not review supplements for safety or effectiveness before they are sold. When researchers pool the trials, most popular weight-loss supplements produce no meaningful loss or about half a kilogram to two kilograms (roughly 1 to 4 pounds) more than placebo, and some carry real risks, from liver injury to hidden prescription drugs. This hub rates each one by evidence so you can see what is established and what is marketing (checked on 2026-10-06).
InstaTuck sells no supplements and links to no sellers; our ratings are editorial and never paid. This page is consumer education, not advice to take or avoid any product. Supplements can interact with medicines and health conditions, so please research, talk with a doctor or pharmacist, and get evaluated before you start one, especially if you take prescription medicines, are pregnant or breastfeeding, or have liver, kidney or heart problems.
Start here: do these next 1-2-3
- Look up the evidence. Check the table below: is the weight-loss claim established, partly established or not established?
- Check for interactions. Bring the product to your pharmacist with the list of everything you take. Berberine, green tea extract and stimulant blends all interact with medicines.
- Compare with approved options. If your goal is substantial weight loss, ask a clinician about approaches with stronger evidence: see how to lose weight and FDA-approved medications.
How supplements are regulated
The FDA says it “doesn’t approve dietary supplements”: by statute, it does not approve them for safety and effectiveness, and many can be marketed without even notifying the agency. Companies are responsible for making sure their products are safe and properly labeled and for following good manufacturing practices. For certain “new dietary ingredients” not sold in the U.S. before October 15, 1994, companies must send the FDA a safety notification at least 75 days before marketing. The FDA can act after a product is on the market when safety problems arise.
Supplements and the FDA
- 0dietary supplements FDA approved for weight loss; the FDA does not approve supplementsFDA, Is it really FDA approved?
- 2004year the FDA banned supplements containing ephedra because of serious health risksNCCIH
- 400 mgdaily caffeine the FDA cites as not generally linked to negative effects in most adults; many "fat burners" are caffeine-basedFDA
Checked on October 6, 2026
How we rate the evidence
| Badge | What it means on InstaTuck |
|---|---|
| High | Consistent, well-designed trials show a meaningful effect on weight |
| Moderate | Several trials agree, but the effect is small or the trials have limits |
| Limited | Small, short or conflicting trials; pooled effects small or unclear |
| Emerging | Early research only |
| Not supported | Good trials show no meaningful weight effect, or there is almost no research |
Weight-loss supplements rated
| Supplement | Weight claim established? | Evidence | What pooled trials or NIH reviews show | Main safety concerns |
|---|---|---|---|---|
| Fiber (psyllium, glucomannan, viscous fiber) | Partly | Moderate | Viscous fiber: -0.33 kg in 62 trials; psyllium and glucomannan reviews conflict | Choking without enough fluid; separate from other medicines |
| Berberine | Partly | Limited | Three meta-analyses: -0.11 kg (not significant), -0.88 kg and -2.07 kg | Drug interactions (cyclosporine, diabetes medicines, CYP3A drugs); constipation |
| Green tea extract | No | Limited | Cochrane: -0.04 kg outside Japan; NCCIH: at most a modest effect | Rare liver injury, especially with extracts in pills |
| Creatine | No (not a weight-loss supplement) | Not supported for weight loss | With strength training: small drop in body-fat percentage but no change in fat mass in adults under 50; small gains in lean mass and strength in postmenopausal women | Water weight gain early on; generally well tolerated in studies |
| Garcinia cambogia (HCA) | No | Limited | -0.88 kg in 9 trials; clinical relevance uncertain | Digestive effects |
| Conjugated linoleic acid (CLA) | No | Limited | -0.70 kg in long-term trials; “not convincingly” relevant | Constipation, diarrhea, soft stools |
| Chromium | No | Limited | -0.50 kg in 11 trials, high heterogeneity | Watery stools, vertigo, headaches, hives |
| Bitter orange (synephrine) | No | Not supported | Effects on weight unclear (NCCIH) | Heart rhythm problems, heart attacks and strokes reported with multi-ingredient products |
| Yohimbe | No | Not supported | Not enough research for any condition, including obesity (NCCIH) | Irregular heartbeat, blood pressure problems, heart attacks, seizures |
| Acai berry | No | Not supported | Not shown to produce meaningful weight loss (NCCIH) | Not well studied |
| “Fat burner” blends | No | Not supported | Rated by ingredient; blends rarely tested as sold | Stimulant overload; hidden drugs found by the FDA |
Hidden drugs: the FDA’s tainted-product warnings
The FDA warns that products marketed as supplements, often promoted for weight loss, sexual enhancement, pain relief or bodybuilding and labeled “all natural”, can contain hidden drug ingredients. In weight-loss products, its laboratory tests have found sibutramine (the active ingredient of Meridia, withdrawn from the U.S. market in December 2010 for heart attack and stroke risk), the stimulant fenproporex, the antidepressant fluoxetine, the diuretics bumetanide and furosemide, the seizure drug phenytoin, the unapproved drugs rimonabant and cetilistat, and phenolphthalein, a former laxative ingredient the FDA reclassified in 1999 over cancer concerns. As recently as September 15, 2026, the FDA warned about a weight-loss product sold online that contained undeclared sibutramine. The agency says its health-fraud database covers only a small fraction of contaminated products, so a product missing from the list is not proof that it is safe.
The FDA also warns about DMAA, an amphetamine derivative sold in weight-loss and workout products and sometimes labeled “geranium extract”. DMAA is not a dietary ingredient; products containing it are illegal, and it can raise blood pressure and cause heart problems including heart attack. Our fat burners guide covers stimulant ingredients in detail.
Interactions worth knowing
- Berberine raised exposure to the transplant drug cyclosporine in kidney-transplant patients, and goldenseal (a berberine source) lowered metformin levels by about 25% in an NIH-funded study. See berberine.
- Green tea in large amounts lowered levels of the heart drug nadolol and the cholesterol drug atorvastatin, and interacted with raloxifene, NCCIH reports.
- Psyllium and other bulk fibers can affect how other drugs are absorbed; the Metamucil Drug Facts label says to take it 2 or more hours before or after other drugs.
- Yohimbe should not be used with MAOI or tricyclic antidepressants, according to NCCIH.
- Stimulant blends and phentermine: the phentermine label says the safety of combining it with other weight-loss products, including over-the-counter and herbal ones, has not been established.
Who should be extra careful
| If you are… | What the sources say |
|---|---|
| Pregnant or breastfeeding | NCCIH: do not use goldenseal (a berberine source), and its berberine can harm newborns; bitter orange may not be safe; oral yohimbe might be unsafe; keep caffeine, including from green tea, moderate. |
| Living with liver disease | Green tea extract has been linked to rare liver injury, and USP’s caution says not to use it with liver problems. |
| Living with heart disease or high blood pressure | Stimulant ingredients (bitter orange, yohimbe, high caffeine, DMAA) have been linked to heart rhythm problems, raised blood pressure and heart attacks. |
| Taking diabetes medicines | Berberine lowers blood sugar and can add to diabetes medicines; goldenseal lowered metformin levels. |
| Taking transplant, heart or cholesterol medicines | Berberine raised cyclosporine exposure; green tea lowered nadolol and atorvastatin levels. |
| Taking any daily medicine | Bulk fibers such as psyllium should be taken 2 or more hours apart from other drugs. |
If something goes wrong
Stop the product and contact a clinician if you notice symptoms such as chest pain, a racing heart, severe headache, yellowing skin or eyes, dark urine or severe stomach pain; call 911 for emergencies. Keep the bottle so the clinician can see exactly what you took. The FDA asks consumers and health professionals to report side effects from supplements and tainted products to its MedWatch Safety Information and Adverse Event Reporting Program. Reports help the agency spot dangerous products sooner.
How to spot a misleading supplement claim
Five checks before you buy
- Too good to be true?NCCIH advises caution with "quick and effective" or "totally safe" claims.
- Testimonials, not trialsPersonal stories and before-and-after photos are not evidence.
- "Natural" is not a safety labelThe FDA finds hidden drugs most often in products sold as all natural.
- Compare with the researchLook up the ingredient here; pooled trials are better than single studies.
- Ask a professionalA pharmacist can check the label against your medicines in minutes.
Supplements with evidence for other goals
Some supplements have evidence for something other than weight loss. Creatine, combined with strength training, has evidence for strength and lean mass, which can matter while losing weight; see creatine and body recomposition. Fiber supplements can help people who fall short of the FDA Daily Value of 28 g of fiber. Protein powders are foods, not weight-loss supplements; our protein shakes guide covers them.
Approaches with stronger evidence
If you are looking for an appetite or weight effect, compare these pages with the supplement ratings above: appetite suppressants (prescription options and supplement claims), weight-loss pills, the oral GLP-1 pills guide and diets rated by evidence. The calorie calculator and Find My Options can help you plan, and the status badges guide explains the difference between “FDA approved” and “dietary supplement”.
All supplement pages
4 results
Dietary supplement: not FDA approvedEvidence: LimitedBerberine for Weight Loss: evidence, risks and interactionsEvidence: Limited
Dietary supplement: not FDA approvedEvidence: Not supportedCreatine for Women: strength, recomposition and safetyEvidence: Not supported
Dietary supplement: not FDA approvedEvidence: ModerateFiber Supplements for Weight Loss: psyllium, glucomannan and moreEvidence: Moderate
Dietary supplement: not FDA approvedEvidence: LimitedGreen Tea Extract: small effects and liver warningsEvidence: LimitedBadges come from the FDA label or FDA records and show the date we last checked. Listing order is never paid for.
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- Could this supplement interact with any medicine I take or any condition I have?
- Is there an approach with stronger evidence for my goal?
- Is this product safe for me if I am pregnant, breastfeeding or have liver or kidney problems?
- What side effects should make me stop and call you?
- Should I bring the bottle so you can check the label and dose?
Frequently asked questions
Do weight-loss supplements work?
Most show no meaningful effect when trials are pooled, and the rest show small effects of about half a kilogram to two kilograms more than placebo. None is FDA approved for weight loss.
What is the most effective weight-loss supplement?
No supplement has strong evidence. Viscous fiber has the most consistent, though modest, effect (-0.33 kg across 62 trials). Approved medicines and lifestyle programs have far stronger evidence.
Are weight-loss supplements FDA approved?
No. The FDA says it does not approve dietary supplements for safety and effectiveness. Companies are responsible for their products' safety and labels.
Are weight-loss supplements safe?
Many have not been tested for safety, NCCIH says. Some have caused liver injury or heart problems, and the FDA has found products hiding prescription drugs such as sibutramine.
Can I take supplements with Wegovy or other GLP-1 medicines?
Ask your prescriber or pharmacist first. Supplements such as berberine can lower blood sugar or change how medicines are processed, and none replaces a prescription treatment.
Is berberine like Ozempic?
No. Berberine is a plant compound sold as a supplement; pooled trials show small, inconsistent weight effects and it can interact with medicines. Ozempic is an FDA-approved prescription drug for type 2 diabetes.
Does creatine help with weight loss?
Creatine is not a weight-loss supplement. With strength training it can help strength and lean mass, and it often adds some water weight at first.
How can I tell if a supplement contains hidden drugs?
You usually cannot tell by looking. Check the FDA health-fraud database, avoid products with exaggerated claims, and remember that the database lists only a fraction of contaminated products.
References
- Is it really ‘FDA approved’?. U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
- 6 Things To Know About Dietary Supplements Marketed for Weight Loss. National Center for Complementary and Integrative Health (NIH). (accessed October 6, 2026) Government page
- Spilling the beans: how much caffeine is too much?. U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
- Questions and answers about FDA’s initiative against contaminated weight loss products. U.S. Food and Drug Administration. (accessed October 6, 2026) Government page
- Avoiding products contaminated with hidden ingredients. U.S. Food and Drug Administration. (accessed October 6, 2026) Government page
- FDA notification: weight-loss product may be harmful due to hidden ingredient (sibutramine). U.S. Food and Drug Administration, 2026. (accessed October 6, 2026) Government page
- DMAA in products marketed as dietary supplements. U.S. Food and Drug Administration. (accessed October 6, 2026) Government page
- Green tea: usefulness and safety. NCCIH (NIH). (accessed October 6, 2026) Government page
- Bitter orange: usefulness and safety. NCCIH (NIH). (accessed October 6, 2026) Government page
- Yohimbe: usefulness and safety. NCCIH (NIH). (accessed October 6, 2026) Government page
- Goldenseal: usefulness and safety. NCCIH (NIH). (accessed October 6, 2026) Government page
- Jurgens TM, Whelan AM, Killian L, et al.. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database of Systematic Reviews, 2012. doi:10.1002/14651858.CD008650.pub2 · PMID 23235664 (accessed October 7, 2026) Meta-analysis
- Onakpoya I, Posadzki P, Ernst E. The efficacy of glucomannan supplementation in overweight and obesity. Journal of the American College of Nutrition, 2014. doi:10.1080/07315724.2014.870013 · PMID 24533610 (accessed October 7, 2026) Meta-analysis
- Jovanovski E, Mazhar N, Komishon A, et al.. Can dietary viscous fiber affect body weight independently of an energy-restrictive diet?. American Journal of Clinical Nutrition, 2020. doi:10.1093/ajcn/nqz292 · PMID 31897475 (accessed October 7, 2026) Meta-analysis
- Onakpoya I, Posadzki P, Ernst E. Chromium supplementation in overweight and obesity: a systematic review and meta-analysis. Obesity Reviews, 2013. PMID 23495911 (accessed October 6, 2026) Meta-analysis
- Onakpoya IJ, Posadzki PP, Watson LK, et al.. The efficacy of long-term conjugated linoleic acid (CLA) supplementation on body composition. European Journal of Nutrition, 2012. PMID 21990002 (accessed October 6, 2026) Meta-analysis
- Onakpoya I, Hung SK, Perry R, Wider B, Ernst E. The use of Garcinia extract (hydroxycitric acid) as a weight loss supplement. Journal of Obesity, 2011. PMID 21197150 (accessed October 6, 2026) Meta-analysis
- Elahi Vahed I, Shahir-Roudi E, Nojumi S, et al.. The effect of berberine on obesity indices: a systematic review and meta-analysis. International Journal of Obesity, 2026. doi:10.1038/s41366-025-01943-x · PMID 41310257 (accessed October 6, 2026) Meta-analysis
- Xiong P, Niu L, Talaei S, et al.. The effect of berberine supplementation on obesity indices: a dose-response meta-analysis. Complementary Therapies in Clinical Practice, 2020. doi:10.1016/j.ctcp.2020.101113 · PMID 32379652 (accessed October 6, 2026) Meta-analysis
- Asbaghi O, Ghanbari N, Shekari M, et al.. The effect of berberine supplementation on obesity parameters, inflammation and liver function enzymes. Clinical Nutrition ESPEN, 2020. doi:10.1016/j.clnesp.2020.04.010 · PMID 32690176 (accessed October 6, 2026) Meta-analysis
- Berberine-drug interactions: mechanisms, clinical relevance and risk stratification (narrative review). Pharmaceuticals, 2026. doi:10.3390/ph19081313 · PMID 42653808 (accessed October 6, 2026) Review
- Candow DG, Prokopidis K, Forbes SC, et al.. Resistance exercise and creatine supplementation on fat mass in adults under 50 years of age: a systematic review and meta-analysis. Nutrients, 2023. doi:10.3390/nu15204343 · PMID 37892421 (accessed October 6, 2026) Meta-analysis
- Naddafha S, Antonio J, Kreider RB, Stout JR. Creatine monohydrate for lean mass, strength, and bone density in postmenopausal women: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 2026. doi:10.1080/15502783.2026.2668435 · PMID 42141930 (accessed October 6, 2026) Meta-analysis
- LOMAIRA (phentermine hydrochloride) tablets: prescribing information. via DailyMed. (accessed October 6, 2026) Drug label
- Wilding JPH, Batterham RL, Calanna S, et al.. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine, 2021. doi:10.1056/NEJMoa2032183 · PMID 33567185 · NCT03548935 (accessed October 7, 2026) Randomized trial
- Oketch-Rabah HA, Roe AL, Rider CV, et al.. United States Pharmacopeia (USP) comprehensive review of the hepatotoxicity of green tea extracts. Toxicology Reports, 2020. doi:10.1016/j.toxrep.2020.02.008 · PMID 32140423 (accessed October 6, 2026) Review
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Facts checked on October 6, 2026
Educational information, not medical advice. Talk with a qualified healthcare professional about your own situation. In an emergency call 911.