Herbs and Supplements for Weight Loss: What the Trials Show (and Why It Is Not Much)
The herbs and supplements with the best evidence for weight loss are green tea extract, glucomannan and berberine, followed by psyllium, L-carnitine and chromium, and the honest headline is that none of them does much. In randomised trials lasting 8 to 16 weeks, the best of them produce 1 to 2 kg (2 to 4 lb) more weight loss than placebo, and the Cochrane review of green tea called the difference "not clinically important". Nothing on this list earns a Strong rating for weight loss. For comparison, a sustained 500 kcal/day deficit loses about 0.5 kg a week, and semaglutide 2.4 mg produced 14.9% body-weight loss over 68 weeks in the STEP 1 trial. Supplements are a rounding error next to either.
This guide is for adults who are already changing what they eat and how much they move and want to know whether anything in a bottle adds to that, and for people who want to know which products are a waste of money or a danger. It is not for anyone hoping a capsule will replace a calorie deficit; it will not. If you have a BMI over 30, or over 27 with diabetes, high blood pressure or sleep apnoea, ask a clinician about prescribed options, which now include GLP-1 drugs with 10 to 20% average weight loss. If you have lost weight without trying, or have a history of an eating disorder, see a clinician rather than reading on.
A warning before the list: the weight-loss supplement category has the worst adulteration record of any. The FDA has found hundreds of 'fat burner' and 'herbal slimming' products laced with sibutramine (a withdrawn appetite drug), phenolphthalein, fluoxetine, or DNP, which has killed people. Products sold on social media or through overseas websites are the highest risk. Buy single ingredients from reputable brands with third-party testing, or buy nothing.
Quick answer
- Green tea extract — about 1.3 kg more loss than placebo over 12 weeks in pooled trials; Cochrane calls the effect not clinically important
- Glucomannan — a viscous fibre that fills the stomach; about 0.8 kg extra loss at 3 g/day with a reduced-calorie diet
- Berberine — around 2 kg of extra loss over 12 weeks in people with metabolic syndrome; the most 'drug-like' option
- Psyllium — 10–15 g/day before meals adds modest fullness and about 1–2 kg over 3 months in overweight adults
- L-carnitine — about 1.2 kg extra loss across 37 trials; works only in people who are overweight, not the already lean
- Chromium picolinate — roughly 1 kg over 12–16 weeks in the Cochrane review, from low-quality trials
The 10 best herbs and supplements for weight loss
Ranked by the strength of human evidence. Strong = multiple trials or a meta-analysis. Moderate = a few small trials. Preliminary = early or animal data.
Green tea catechins raise fat oxidation slightly, and the effect depends on caffeine being present. A 2009 meta-analysis of 11 trials found green tea produced 1.31 kg more weight loss than placebo over roughly 12 weeks, with a smaller effect in habitual high-caffeine users and in trials of East Asian participants versus Western ones. The 2012 Cochrane review of 14 trials found losses ranging from 0.2 to 3.5 kg, a pooled difference of under 1 kg, and judged the effect small and not clinically important. It remains the most-studied item here, which says something about the field.
- Key evidence
- 2012 Cochrane review of 14 RCTs (Jurgens et al.); 2009 meta-analysis of 11 trials (Hursel et al.)
- Studied dose
- 250–500 mg/day of a catechin extract providing 200–300 mg EGCG with 100–200 mg caffeine, taken with meals, 12 weeks
- Best for
- People who do not already consume a lot of caffeine and want a modest metabolic nudge alongside a calorie deficit
- Cautions
- Concentrated extracts taken fasting, especially above 800 mg EGCG/day, have caused liver injury; take with food and stop if urine darkens. The caffeine raises blood pressure and interacts with stimulants, some antidepressants and anxiety; it reduces iron absorption.
Glucomannan absorbs up to 50 times its weight in water, forming a gel that slows stomach emptying and blunts hunger. A 2008 meta-analysis of 14 trials found about 0.8 kg more weight loss than placebo over 5 weeks, alongside falls in LDL and fasting glucose; a 2014 meta-analysis restricted to 8 better-quality trials found no significant effect (0.2 kg), and a well-run 2013 US trial of 1.33 g three times a day for 8 weeks found nothing at all. The European regulator accepts a weight-loss claim only at 3 g/day combined with a reduced-calorie diet, which is a fair summary: a small assist, not an agent.
- Key evidence
- 2014 meta-analysis of 8 RCTs (Onakpoya et al.); EFSA opinion supporting a claim at 3 g/day with an energy-restricted diet
- Studied dose
- 1 g with 1–2 glasses of water, 30–60 minutes before each of 3 meals (3 g/day), 8–12 weeks
- Best for
- People whose main obstacle is hunger between meals or large portions; those with raised LDL or glucose as well
- Cautions
- Tablets have caused oesophageal and bowel obstruction when swallowed with too little water; use capsules or powder and drink generously. It reduces the absorption of oral drugs taken at the same time, including sulfonylureas and some thyroid medication; separate by 1–2 hours.
Berberine
Moderate evidenceBerberine is marketed as 'nature's Ozempic', which it is not: it works on AMPK and gut bacteria, not GLP-1 receptors, and the effect is a tenth as large. A 2020 meta-analysis of 12 trials in overweight adults found about 2 kg more weight loss, a BMI reduction of around 0.5 and a waist reduction of about 1.3 cm versus control over 8–16 weeks, with better results in people with metabolic syndrome or fatty liver. A 12-week pilot in obese adults at 500 mg three times a day found 2.3 kg of loss with improved lipids. That is the best number on this page, and still modest.
- Key evidence
- 2020 meta-analysis of 12 RCTs on obesity parameters (Asbaghi et al., Clin Nutr ESPEN)
- Studied dose
- 500 mg of berberine HCl 2–3 times daily with meals, 12 weeks
- Best for
- Overweight with insulin resistance, prediabetes, PCOS or fatty liver, where the metabolic benefits justify it even if the scale barely moves
- Cautions
- Inhibits CYP3A4 and CYP2D6, raising levels of many drugs (cyclosporine, some statins, calcium-channel blockers); causes constipation or diarrhoea in up to a third of users; additive with diabetes medication. Avoid in pregnancy and breastfeeding.
Psyllium's viscous fibre increases fullness and slows glucose absorption, and unlike glucomannan it has not failed in a well-run trial. A 2020 meta-analysis of 22 trials found psyllium reduced body weight by about 2 kg, BMI by 0.8 and waist circumference by about 2 cm, with the effect confined to people who were overweight or obese and taking it for more than 12 weeks. Its real value is that it reliably lowers LDL and glucose while you lose weight, so you get something even if the scale is stubborn.
- Key evidence
- 2020 meta-analysis of 22 RCTs in overweight and obese adults (Darooghegi Mofrad et al.)
- Studied dose
- 5–7 g of psyllium husk in a full glass of water, 15–30 minutes before 2–3 meals (10–15 g/day), 12 weeks or longer
- Best for
- Overweight adults who also have high LDL, raised glucose or constipation
- Cautions
- Must be taken with plenty of water; can reduce absorption of medicines taken at the same time (levothyroxine, lithium, digoxin), so separate by 2 hours. Avoid with swallowing difficulties or bowel narrowing.
L-carnitine
Moderate evidenceL-carnitine shuttles fatty acids into mitochondria, which sounds like a fat burner but is rarely the rate-limiting step. A 2020 meta-analysis of 37 randomised trials (2,292 participants) found 1.21 kg more weight loss and a BMI reduction of 0.24 versus placebo, with the effect present only in overweight and obese participants and no benefit from doses above 2 g/day. An earlier 2016 meta-analysis of 9 trials gave 1.33 kg. It does not increase fat burning during exercise in people who are not deficient, which is most people.
- Key evidence
- 2020 meta-analysis of 37 RCTs, 2,292 participants (Talenezhad et al., Clin Nutr ESPEN)
- Studied dose
- 2 g/day of L-carnitine tartrate or L-carnitine, with food, 12 weeks
- Best for
- Overweight adults, vegetarians and vegans (who have lower stores), and people over 60 with low muscle mass
- Cautions
- Gut bacteria convert carnitine to TMAO, a compound linked to cardiovascular risk in observational studies; it can cause a fishy body odour and increase seizure frequency in people with epilepsy. May enhance warfarin's effect.
Chromium picolinate
Moderate evidenceChromium is sold for cravings and 'carb metabolism'. The 2013 Cochrane review of 9 trials in overweight adults found about 1.1 kg more weight loss over 12–16 weeks, but rated the evidence low quality and noted no dose-response and no effect on body composition. A 2013 meta-analysis of 11 trials found 0.5 kg. A trial in people with binge-eating found 1,000 mcg/day reduced binge frequency a little more than placebo, which is the only appetite-specific signal. If you have type 2 diabetes it may help glucose; for weight alone it is not worth much.
- Key evidence
- 2013 Cochrane review of 9 RCTs in overweight adults (Tian et al.)
- Studied dose
- 200–1,000 mcg/day of chromium picolinate with food, 12–16 weeks
- Best for
- Overweight with type 2 diabetes or prediabetes; people with strong carbohydrate cravings
- Cautions
- Adds to the effect of insulin and sulfonylureas; rare reports of kidney injury at high doses. Keep below 1,000 mcg/day and avoid with kidney disease.
Chilli compounds activate TRPV1 receptors, raising energy expenditure by about 50 kcal/day and reducing intake by about 74 kcal/day in a 2012 systematic review of 20 trials, and increasing brown-fat activity in imaging studies. Over 12 weeks that works out to roughly 0.5 kg, and a 2018 meta-analysis of 8 trials confirmed a small, significant reduction in body weight and fat that is unlikely to be noticed by the person taking it. Non-pungent capsinoids (from sweet CH-19 peppers) give the same effect without the burn.
- Key evidence
- 2012 systematic review of 20 trials (Whiting et al., Appetite); 2018 meta-analysis of 8 RCTs
- Studied dose
- 2–10 mg/day of capsaicinoids from cayenne, or 6 mg/day of capsinoids, with food, 12 weeks
- Best for
- People who already like spicy food and want a tiny thermogenic edge; not for anyone with reflux or IBS
- Cautions
- Causes stomach pain, reflux and loose stools at higher doses; may increase the absorption of some drugs and the bleeding risk with anticoagulants. Avoid before endoscopy or bowel surgery.
Cinnamon improves insulin sensitivity, which indirectly affects fat storage. A 2020 meta-analysis of 21 trials (1,480 participants) found cinnamon produced about 1 kg more weight loss, a 0.4-point BMI reduction and a 2.4 cm smaller waist versus control, with larger effects at 3 g/day or more, in people under 50 and in those with a starting BMI of 30 or over. Most trials were from Iran and short, so the number is soft. It is reasonable if you also have raised fasting glucose; on its own it is not a weight-loss tool.
- Key evidence
- 2020 meta-analysis of 21 RCTs, 1,480 participants (Mousavi et al., Clinical Nutrition)
- Studied dose
- 1.5–3 g/day of Ceylon cinnamon powder, or a standardised water extract, 12 weeks
- Best for
- Overweight with prediabetes or PCOS, used as a food rather than a capsule
- Cautions
- Cassia cinnamon's coumarin can harm the liver at daily doses above about 3 g; use Ceylon. Adds to glucose-lowering medication; avoid high doses in pregnancy.
Probiotics (Lactobacillus strains)
Preliminary evidenceCertain strains, notably Lactobacillus gasseri SBT2055 and some L. rhamnosus and L. plantarum strains, reduced visceral fat by 4–9% and body weight by about 1.5% over 12 weeks in Japanese and Canadian trials. A 2018 meta-analysis of 15 randomised trials in overweight and obese adults found probiotics lowered body weight by 0.6 kg, BMI by 0.27 and fat percentage by 0.6 points versus placebo. Effects are strain-specific and disappear within weeks of stopping. The gut-microbiome story is real; the weight effect is tiny.
- Key evidence
- 2018 meta-analysis of 15 RCTs, 957 participants (Borgeraas et al., Obesity Reviews)
- Studied dose
- 1–10 billion CFU/day of a named, trialled strain (for example L. gasseri SBT2055 or L. rhamnosus CGMCC1.3724), 12 weeks
- Best for
- People with central (abdominal) weight gain, bloating or recent antibiotic use
- Cautions
- Avoid in people who are immunocompromised, have a central venous catheter or severe pancreatitis, where live bacteria have caused infections. Generally safe otherwise; bloating in the first week is common.
Inulin and oligofructose
Preliminary evidenceThese prebiotic fibres are fermented in the colon to short-chain fatty acids that raise the satiety hormones PYY and GLP-1. In a 12-week Canadian trial, 21 g/day of oligofructose produced 1.03 kg of weight loss versus a 0.45 kg gain on placebo in 48 overweight adults, with lower ghrelin and reduced calorie intake. An 18-week UK trial of 30 g/day inulin in prediabetes found about 2 kg more loss and reduced liver fat. Two small positive trials, both at doses that cause real bloating.
- Key evidence
- 12-week RCT of oligofructose, n=48 (Parnell and Reimer, Am J Clin Nutr 2009)
- Studied dose
- 10–20 g/day of inulin or oligofructose powder, built up from 5 g over 2 weeks, with food, 12 weeks
- Best for
- People with constipation, low fibre intake or prediabetes who tolerate fermentable fibre
- Cautions
- Gas, bloating and cramping are common above 10 g/day and much worse with IBS; it is a FODMAP, so avoid during a low-FODMAP diet. Fine with most medications.
How to choose
- Fix the deficit first. If you are not already eating fewer calories than you burn, no supplement on this list will do anything; every positive trial above gave the product alongside a diet.
- If hunger between meals is the obstacle, choose a fibre: psyllium or glucomannan before meals, or inulin if constipation is also a problem. These are the cheapest and safest.
- If you have insulin resistance, prediabetes, PCOS or fatty liver, berberine is the one item whose metabolic benefits justify taking it even if weight loss is small; cinnamon and chromium are the budget versions.
- If you want a thermogenic, green tea extract with caffeine or capsaicin are the only ones with any evidence, and together they are worth maybe 100 kcal/day; caffeine alone (100–200 mg) does the same, which is why most 'fat burners' are just caffeine at a premium price.
- Fenugreek fibre (8 g) increases fullness for a few hours in small studies but has no weight-loss trials, and appetite-suppressing herbs like hoodia failed their trials; treat 'appetite herb' claims with suspicion.
- If your BMI is over 30, or over 27 with a weight-related condition, ask a clinician about GLP-1 medication or a structured programme before spending money on supplements; ask AskMN if you want to compare the trial numbers side by side.
What to skip
Garcinia cambogia (hydroxycitric acid)
A 2011 meta-analysis of 9 trials found 0.88 kg more loss than placebo over 2–12 weeks, driven by the worst trials; the best-run 12-week trial of 135 people found no effect. It has also been linked to liver injury, mania and serotonin toxicity with SSRIs, and was an ingredient in reformulated Hydroxycut when that product was withdrawn for liver damage.
'Fat burner' and 'thermogenic' blends
These are mostly caffeine (often 200–400 mg) plus a dozen herbs at trace doses. The caffeine raises heart rate and blood pressure, the herbs do nothing at those amounts, and the category is the single most common source of FDA warnings for hidden sibutramine, DNP and other drugs. Buy plain caffeine if that is what you want.
Raspberry ketones
The only evidence is in mice and cell cultures; there is not a single randomised trial in humans showing weight loss from raspberry ketones alone. The 'fat burning' claim came from a television segment, not a study.
Apple cider vinegar gummies
A 12-week Japanese trial of 15–30 mL of liquid vinegar a day found 1–2 kg of loss, which regained within a month; gummies contain a fraction of that dose plus sugar. No trial has ever tested a gummy.
Safety and when to see a clinician
- Adulteration is the main danger. The FDA maintains a list of tainted weight-loss products, most containing undeclared sibutramine, phenolphthalein, fluoxetine or DNP. If a product promises rapid loss, is sold mainly through social media, or has a label in a language you cannot read, do not take it.
- Stimulants (caffeine, synephrine, yohimbine, and green tea extract taken with caffeine) raise blood pressure and heart rate; avoid them with hypertension, arrhythmias, anxiety disorders, MAOI antidepressants and during pregnancy.
- Liver: green tea extract taken fasted at high doses and garcinia have both caused liver injury requiring transplant in rare cases. Stop any supplement and see a clinician if you develop dark urine, pale stools, yellow eyes or right-sided abdominal pain.
- Fibres (glucomannan, psyllium) reduce the absorption of medicines taken at the same time, and berberine raises the blood levels of many drugs; separate fibres by 2 hours and check berberine with a pharmacist.
- If you take insulin or sulfonylureas, berberine, chromium, cinnamon and fibres all lower glucose and can cause hypoglycaemia as you lose weight; your medication may need reducing, which is your prescriber's job.
- See a clinician if you have lost weight without trying, have a history of disordered eating, are pregnant or breastfeeding, are under 18, or have a BMI over 30 and have not had a conversation about prescription options.
What matters as much as any herb
- A 500 kcal/day deficit, achieved however you can stick to it, loses about 0.5 kg a week; that is 6 kg in 12 weeks, versus 1–2 kg from the best supplement here.
- Protein at 1.2–1.6 g per kg of body weight a day increases fullness, preserves muscle while dieting and raises the energy cost of digestion more than any thermogenic herb.
- Sleeping under 7 hours raises ghrelin, lowers leptin and adds roughly 300 kcal of intake a day in controlled studies; in one trial, extending sleep by an hour cut intake by 270 kcal/day without any other change.
- Resistance training 2–3 times a week keeps the weight you lose coming from fat rather than muscle, which protects your metabolic rate over the long run.
- Weighing yourself daily and tracking intake for even a few weeks roughly doubles weight loss in programme trials; it is free and more effective than anything in a capsule.
Frequently asked questions
What is the most effective herb for weight loss?
Berberine has the largest effect in pooled trials, around 2 kg over 12 weeks in people with metabolic syndrome, followed by green tea extract and psyllium at 1–2 kg. None of them compares to a calorie deficit or to prescribed medication, and the gap is not close.
Is berberine really 'nature's Ozempic'?
No. Semaglutide produced 14.9% body-weight loss (about 15 kg) over 68 weeks in STEP 1; berberine produces about 2 kg over 12 weeks and works through different pathways. Berberine is a reasonable metabolic supplement for insulin resistance; it is not a weight-loss drug.
Which herbs boost metabolism?
Green tea catechins with caffeine and capsaicin raise energy expenditure by roughly 50–100 kcal/day, which is the equivalent of a 10-minute walk. Nothing herbal raises resting metabolism by more than that. Building muscle through resistance training is the only reliable way to raise it.
What herbs curb appetite?
The best evidence is for fibres rather than herbs: glucomannan and psyllium taken before meals with water increase fullness and reduce intake modestly. Fenugreek fibre and inulin show the same in small studies. Hoodia, the famous 'appetite herb', failed its one proper trial and caused nausea and raised blood pressure.
Are weight loss supplements safe?
Single ingredients from reputable brands at the doses above are generally safe for healthy adults, with the cautions listed. Multi-ingredient 'fat burners' and products sold through social media or overseas sites are frequently adulterated with prescription drugs and have caused liver failure, strokes and deaths. The category as a whole is the most dangerous in the supplement aisle.
How much weight can I lose with green tea extract?
About 1 kg more than you would lose without it over 12 weeks, according to the Cochrane review, and less if you already drink a lot of caffeine. It will not produce visible results on its own.
Should I try supplements before GLP-1 medication?
If your BMI is under 27 and you have no weight-related conditions, supplements and diet are the appropriate route, with modest expectations. If your BMI is over 30, or over 27 with diabetes, hypertension or sleep apnoea, GLP-1 drugs have 10–20% average weight loss and outcome data; spending months on supplements first delays effective treatment.
References
- 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)
- Onakpoya I, Posadzki P, Ernst E. The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials. Journal of the American College of Nutrition (2014)
- Asbaghi O, Ghanbari N, Shekari M, et al.. The effect of berberine supplementation on obesity parameters, inflammation and liver function enzymes: a systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition ESPEN (2020)
- Tian H, Guo X, Wang X, et al.. Chromium picolinate supplementation for overweight or obese adults. Cochrane Database of Systematic Reviews (2013)
- Talenezhad N, Mohammadi M, Ramezani-Jolfaie N, et al.. Effects of l-carnitine supplementation on weight loss and body composition: a systematic review and meta-analysis of 37 randomized controlled clinical trials with dose-response analysis. Clinical Nutrition ESPEN (2020)
- Mousavi SM, Rahmani J, Kord-Varkaneh H, et al.. Cinnamon supplementation positively affects obesity: a systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition (2020)
- Borgeraas H, Johnson LK, Skattebu J, et al.. Effects of probiotics on body weight, body mass index, fat mass and fat percentage in subjects with overweight or obesity: a systematic review and meta-analysis of randomized controlled trials. Obesity Reviews (2018)
- Parnell JA, Reimer RA. Weight loss during oligofructose supplementation is associated with decreased ghrelin and increased peptide YY in overweight and obese adults. American Journal of Clinical Nutrition (2009)
- Whiting S, Derbyshire E, Tiwari BK. Capsaicinoids and capsinoids. A potential role for weight management? A systematic review of the evidence. Appetite (2012)
- Onakpoya I, Hung SK, Perry R, et al.. The use of Garcinia extract (hydroxycitric acid) as a weight loss supplement: a systematic review and meta-analysis of randomised clinical trials. Journal of Obesity (2011)
- 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)
- NIH Office of Dietary Supplements. Dietary Supplements for Weight Loss: Fact Sheet for Health Professionals (2022)View source
Related conditions
More guides
Not sure which one fits you?
Ask AskMN. It knows these studies, checks interactions with the medications you tell it about, and it is free and unlimited, no account needed.
Ask about weight lossThis guide is educational and is not medical advice. Herbs and supplements can interact with prescription medicines and are not regulated like drugs. Talk with a clinician or pharmacist before starting anything new, especially if you are pregnant, breastfeeding, have a chronic condition, or take medication.