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Weight-Loss Supplements: What the Trials Show, and Which Ones Can Hurt You

Most weight-loss supplements do little. In pooled trials the better ones added about 1 to 2 kg (2 to 4 pounds) of loss over a few months, less than reviewers count as meaningful. Soluble fiber has the most consistent small effect (grade A). Green tea, garcinia and bitter orange showed little or none, and the best-known green coffee trial was retracted. Some diet pills hide prescription drugs, so check FDA warnings before you buy.

Published Updated How we grade evidenceEditorial policy

The short version

  • Most weight-loss supplements add little or nothing: of 315 trials, only 52 were reliable enough to judge, and only 16 of those found a real weight difference (Batsis 2021).
  • Soluble fiber supplements helped a little: about 1.25 kg (under 3 pounds) more loss across 27 trials. Grade A (Huwiler 2022).
  • Green tea and garcinia made no clinically useful difference. Grade B (Jurgens 2012; Maunder 2020).
  • Green coffee rests on weak trials, and its best-known study was retracted. Grade C (Onakpoya 2011).
  • Bitter orange raised blood pressure without helping weight. Grade B (Koncz 2022).
  • Diet pills are a common hiding place for drugs: 317 weight-loss products drew FDA warnings over 10 years (Tucker 2018).

If weight is your goal this year, the honest summary is that supplements are a sideshow. Two large reviews set 2.5 kg (about 5.5 pounds) as the smallest loss that matters, and no supplement reached it reliably (Bessell 2021; Maunder 2020). For fat versus muscle, see our body composition guide. For prescription weight-loss drugs, see supplements on GLP-1 medicines.

Do weight-loss supplements actually work?

Barely. A 2021 review found 315 randomized trials of 14 supplements and therapies. Only 52 were at low risk of bias with enough data, and only 16 of those showed a significant weight difference, from 0.3 to 4.93 kg (Batsis 2021). A 2023 analysis of 111 trials (6,171 adults) concluded that the supplements it ranked "can result in a small weight loss" (Shahinfar 2023).

SupplementWhat trials foundExtra loss vs placeboGrade
Soluble fiber (all types)Small, consistent lossAbout 1.25 kgA
PsylliumSmall loss when taken before mealsAbout 2.1 kgB
ChitosanSmall in poor trials, minimal in good onesUnder 2 kgB
White kidney bean extractSmall lossAbout 1.6 kgB
BerberineBMI slightly lower, not robust; waist smallerBMI about 0.4; waist about 3 cmC
ChromiumSmall, of doubtful valueAbout 1.1 kgB
CLAVery smallAbout 0.35 kgB
Green teaNone outside JapanAbout 0 kgB (no effect)
GarciniaNone to very smallUnder 1 kgB (no effect)
Bitter orangeNo significant loss; higher blood pressureNot significantB (no effect)
Green coffee, apple cider vinegar, triphalaSmall, weak or disputed trialsUnclearC
Raspberry ketoneNo trial of it aloneUnknownD

Does fiber help you lose weight?

Grade A for a small effect. Across 27 trials (1,428 people) lasting at least 12 weeks, soluble fiber supplements led to 1.25 kg more weight loss than control, with smaller waists and better insulin levels (Huwiler 2022). Psyllium taken just before meals (about 10.8 g a day) added about 2.1 kg over roughly 5 months in 6 trials (354 people); the review's authors declared that they are employees of a company that sells psyllium (Gibb 2023). Glucomannan, a fiber from konjac root, looks weaker: 8 pooled trials showed no significant loss (Onakpoya 2014), and a later one found 1.27 kg, still short of meaningful (Bessell 2021). Side effects in the glucomannan trials were stomach discomfort, diarrhea and constipation (Onakpoya 2014). See our fiber page and psyllium page.

Does green tea extract help weight loss?

Grade B for no meaningful effect. In a Cochrane review, 6 trials outside Japan (532 people) found an average difference of 0.04 kg after about 12 weeks, essentially nothing (Jurgens 2012). High-dose extracts can also injure the liver; see our supplements and your liver guide and green tea extract page.

Does garcinia cambogia work?

Grade B for little or no effect. Pooling 9 trials, garcinia's hydroxycitric acid added 0.88 kg of loss, an amount the authors called of uncertain clinical relevance (Onakpoya 2011), and a 2020 review of herbal trials found no effect (Maunder 2020). The harm is real: in a US liver-injury registry, 22 people were hurt by garcinia products, often mixed with green tea; 91% were hospitalized, one died and one needed a liver transplant (Vuppalanchi 2022).

Does green coffee extract work for weight loss?

Grade C. An early review pooled 3 trials, all at high risk of bias (Onakpoya 2011). The most publicized green coffee trial was later retracted by its journal (retraction notice, 2014). A 2023 analysis of 3 small trials (103 people) taking at least 500 mg a day of chlorogenic acid found 1.30 kg more loss, and its authors asked for longer trials (Kanchanasurakit 2023). See our green coffee extract page.

Do raspberry ketones work?

Grade D. Our literature search found no human trial that tested raspberry ketone by itself. The one weight trial tested an 8-week blend that also contained caffeine, capsaicin and bitter orange, alongside diet and exercise; 45 of 70 people finished, and weight fell 2.0% vs 0.5% on placebo (Lopez 2013). That says nothing about raspberry ketone itself.

Does apple cider vinegar help weight loss?

Grade C. A widely shared 2024 trial in 120 young people reported weight loss but was retracted in 2025 (Abou-Khalil 2024). A 2025 analysis of 10 trials (789 adults) found a small drop in weight, but that retracted trial is one of the 10 it pooled (Castagna 2025). Treat any benefit as unproven.

Is berberine "nature's Ozempic"?

Grade C for a small, uncertain effect, nowhere near a prescription drug. In 8 placebo-controlled trials of berberine alone, BMI was about 0.4 lower, but not significantly once the 2 weakest trials were left out; waist size was about 3 cm smaller in 4 trials (Liu 2025). A larger 2026 review is not used because its references include a retracted trial and a trial from a research group whose work we exclude, and whether its weight result depends on them can't be checked. It lowers blood sugar, so if you take metformin, read can I take berberine with metformin? and ask your prescriber. See our berberine page.

What about chromium, CLA, chitosan, probiotics and others?

  • Chromium picolinate: 1.1 kg more loss in 6 trials, low-quality evidence of debatable value. Grade B (Tian 2013). See our chromium page.
  • CLA: 0.35 kg across 70 trials, and no fat change in the high-quality ones. Grade B (Asbaghi 2024). See our CLA page.
  • Chitosan: 1.7 kg overall, but minimal in the better trials. Grade B (Jull 2008).
  • White kidney bean extract: 1.62 kg in 8 trials (543 people). Grade B (Shi 2026). See our white kidney bean page.
  • Capsaicin (chili extract): 0.51 kg in 15 trials. Grade B (Zhang 2023).
  • Probiotics: more loss and less belly fat in 8 small trials (412 people). Grade C (Guo 2025).
  • Triphala: 5 small trials found lower weight, and the review calls for large trials. Grade C (Phimarn 2021). Our obesity page grades it A from a pooled analysis we could not trace; we are re-checking that row.

What we'd skip

  • Bitter orange (synephrine). No significant weight loss, and systolic blood pressure rose about 6.4 mmHg with longer use (Koncz 2022).
  • Ephedra. It added about 1 kg a month, but people taking it had 2.2 to 3.6 times the odds of psychiatric symptoms, stomach upset or palpitations (Shekelle 2003); the FDA banned it in supplements in 2004 (NCCIH).
  • Garcinia and green tea "fat burners." No useful loss (Maunder 2020), and serious liver injury in registry cases (Vuppalanchi 2022).
  • Raspberry ketone. No trial of it alone (absence of evidence; see above).
  • Diet pills from online sellers or overseas shipments. Of the adulterated supplements the FDA found in 2014 to 2016, 38.6% came from online sampling and 34.3% from international mail (Tucker 2018).

Safety and interactions

  • Hidden drugs: 317 weight-loss supplements drew FDA warnings for unapproved drugs in the 10 years to 2016, most often sibutramine (269 of them), and some were still sold after the warnings (Tucker 2018). The FDA's current list says weight-loss pills and teas are "likely to be contaminated with dangerous hidden ingredients" and covers only a fraction of them (FDA).
  • Heart symptoms: supplements send about 23,000 Americans to emergency departments each year; among those visits involving palpitations, chest pain or a racing heart, 71.8% were caused by weight-loss or energy products (Geller 2015).
  • Liver: garcinia and green tea extract products have caused severe liver injury (Vuppalanchi 2022); see our liver guide.
  • Medicines: ask your pharmacist how to time a fiber supplement around your medicines. Berberine adds to blood-sugar drugs (see the metformin link above). No interaction studies were found for most other products.
  • Stacks: many products combine several ingredients; check your stack against the upper limits.

When to see a doctor

  • Right away: chest pain, a racing or pounding heartbeat, fainting, or a severe headache after starting a diet product. Call 911 for chest pain.
  • Same day: yellow skin or eyes, or dark urine.
  • Before starting: if you have heart disease, high blood pressure, diabetes, liver or kidney disease, or take prescription medicines. If you have obesity, ask about treatments with stronger evidence, including prescription medicines.

Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. If you are pregnant, breastfeeding or under 18, ask a clinician before using any weight-loss product.

FAQ

What is the best supplement for weight loss? Soluble fiber has the most consistent effect, about 1.25 kg more loss than placebo across 27 trials (grade A). That is small, and no supplement reliably reached the 2.5 kg that reviewers count as meaningful.

Does green coffee extract work? The trials are small and weak (grade C), and the best-known study was retracted. A 2023 analysis of 3 small trials found 1.30 kg more loss.

Does garcinia cambogia work for weight loss? Little or not at all (grade B), and garcinia products have caused severe liver injury, including a death and a liver transplant.

Do raspberry ketones help you lose weight? No human trial has tested raspberry ketone by itself (grade D).

Are weight-loss supplements safe? Many are not checked before sale. The FDA flagged 317 weight-loss supplements with hidden drugs over 10 years, and weight-loss or energy products caused most supplement-related emergency visits for heart symptoms.

Sources

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