Herbs for Weight Loss: Claims Checked
Do herbs and botanical fat burners help with weight loss? What reviews of green tea and other supplements found, plus hidden-drug, stimulant and liver risks.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Weight-loss products carry some of the most serious hidden risks in the supplement aisle. The US FDA says many products sold as diet pills, fat burners, weight-loss supplements and teas are likely to be contaminated with dangerous hidden ingredients, and that its public list covers only a small fraction of them. [1] Green tea extract capsules have been linked to liver injury, and extracts can raise blood pressure. [2] Liver warning signs are listed in Liver Injury Warning Signs From Supplements and Herbs. If you feel in crisis, call or text 988 (US). Restrictive dieting and laxative misuse are covered in Eating Disorders, Weight-Loss Supplements and Laxative Misuse.
The claim as marketed
Labels promise that a plant "burns fat", "melts belly fat" or "speeds metabolism". Common ingredients include green tea (Camellia sinensis (L.) Kuntze [3]), bitter orange, Coleus forskohlii, glucomannan and psyllium. [4] This page checks the claim against reviews, not against product marketing.What the evidence is
| Question | What the source found | Strength of evidence |
|---|---|---|
| Do dietary supplements and "alternative therapies" lead to weight loss? | A systematic review found 315 randomized trials of 14 supplements or therapies. Only 52 were low risk of bias and sufficient to support efficacy, and of those only 16 showed a significant difference in weight (range 0.3 to 4.93 kg). [5] | Mostly insufficient evidence |
| Natural supplements in people with obesity | A critical review of bitter orange, capsinoid, carnitine, chromium picolinate, Coleus forskohlii, conjugated linoleic acid, glucomannan, green tea and psyllium found insufficient evidence of significant weight loss, with a possible exception for one glucomannan fiber form. [4] | Insufficient evidence |
| Green tea preparations, 12 weeks or more | A Cochrane review found a small, non-significant weight loss that is unlikely to be clinically important. Outside Japan, the pooled difference was -0.04 kg. [6] | No good evidence of meaningful benefit |
| Green tea catechins and caffeine | NCCIH says they may have a modest effect on body weight, depending on the product and activity level. [2] | Promising but limited |
| "Thermogenic" fat burners added to diet and exercise | A meta-analysis found limited benefit and responses less than diet and exercise without supplements. [7] | Insufficient evidence |
| Aloe gel by mouth | One small study of a specific product found modest loss of weight and fat in adults with obesity or overweight who had diabetes or prediabetes. [8] | Promising but limited (one small study) |
Those review results come from many different plants, extracts and amounts, so none transfers to a different product.
What a reader can safely do
Check a product against the FDA lists, ask a pharmacist about your medicines, and talk to a clinician about weight, including medical care options in Weight-Loss Medications and Medical Care. The wider claim check is in Weight-Loss Supplements, Fat Burners, Detox Teas and Vinegar. For any supplement, tell your surgical team (before surgery).Frequently asked questions
Does green tea help you lose weight?
A Cochrane review found only a small weight loss that was not statistically significant and not likely to matter clinically. [6]
Are there herbal fat burners that work?
A review of 315 trials found a limited high-quality evidence base for supplements and alternative therapies. [5] A meta-analysis of thermogenic supplements found limited benefit. [7]
Are weight-loss teas and capsules safe?
The FDA warns that many are likely to contain hidden ingredients. [1] Green tea extract capsules have been linked to liver injury. [2]
Can herbs for weight loss harm the liver or kidneys?
A critical review reported liver and kidney failure in some cases. [4]
Is a drink of green tea safe?
NCCIH reports no safety concerns for green tea as a beverage in adults, though it contains caffeine. [2]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
What regulators and agencies say
- FDA: contaminated weight-loss products "pose a serious health risk and are not guaranteed to work." [1] See Hidden Drugs in Supplements.
- NCCIH: green tea as a beverage has had no safety concerns reported for adults, although it contains caffeine. [2]
- FDA (page current as of 2024): about 400 mg of caffeine a day is an amount not generally associated with negative effects for most adults, and caffeine can be added to dietary supplements. [9]
Risks to know
- Liver and kidney. The critical review noted that most side effects were minor to moderate and stomach-related, but liver and kidney failure were seen in some cases. [4] Green tea extract liver injury is uncommon but reported, mostly with tablets or capsules. [2]
- Medicines. High-dose green tea has lowered blood levels of the beta-blocker nadolol, and green tea extract has lowered levels of atorvastatin. [2] See medicine interactions.
- Aloe latex taken by mouth can cause abdominal pain, cramps and diarrhea. [8]
- Pregnancy. Caffeine should stay at moderate levels; ask your clinician. [2]
- Stimulant herbs. See bitter orange, yohimbe and stimulant herbs and ephedra and other restricted ingredients.
References
- FDA, Weight Loss Product Notifications. Read 2026-10-23.
- NCCIH, Green Tea: Usefulness and Safety. Read 2026-10-23.
- GBIF Backbone Taxonomy, Camellia sinensis (L.) Kuntze. Read 2026-10-23.
- The safety and effectiveness of commonly-marketed natural supplements for weight loss in populations with obesity: a critical review of the literature from 2006 to 2016, Crit Rev Food Sci Nutr 2020. Read 2026-10-23.
- Batsis JA et al., A systematic review of dietary supplements and alternative therapies for weight loss, Obesity 2021. Read 2026-10-23.
- Jurgens TM et al., Green tea for weight loss and weight maintenance in overweight or obese adults, Cochrane Database Syst Rev 2012. Read 2026-10-23.
- Comparing effectiveness of fat burners and thermogenic supplements to diet and exercise for weight loss and cardiometabolic health: systematic review and meta-analysis, Nutr Health 2021. Read 2026-10-23.
- NCCIH, Aloe Vera: Usefulness and Safety. Read 2026-10-23.
- FDA, Spilling the Beans: How Much Caffeine is Too Much? (content current as of 08/28/2024). Read 2026-10-23.