Do Weight Loss Supplements Work? What 315 Trials Found

In brief: for most people, weight loss supplements don't work well enough to matter. A 2021 systematic review for The Obesity Society examined 315 randomized trials of 14 types of supplement and alternative therapy. Only 52 were high quality, and just 16 of those found more weight loss than a placebo, between 0.3 and 4.9 kg (0.7 to 10.8 lb). The authors concluded that no product had strong, high-quality evidence behind it.

Do Weight Loss Supplements Work? The Short Answer

The best current evidence says no product reliably works. The review, led by John Batsis and published in the journal Obesity, is one of the widest looks at the research. Its authors searched five medical databases, screened 20,504 records, and kept only randomized controlled trials in adults.

What they found was a weak evidence base:

• Most trials were small and short, often a few weeks to a few months. Very few ran for a year, which is how long major lifestyle trials usually last.
• Many had design problems, such as comparing people only with themselves rather than with a placebo group.
• Industry funding was common, and many trials didn't report who paid for them.
• Where good-quality trials did show an effect, the authors judged the amounts too small to be clinically meaningful.

The review didn't rule out every product forever. It concluded that better, longer and independent trials are needed before any supplement can be recommended.

Results by Supplement

Here is what the high-quality trials (those with a low risk of bias) showed for each product the review summarized:

Supplement or therapy	Trials found	High-quality trials	What the high-quality trials showed
Green tea	38	16	Only 2 found extra loss, 1.5–1.7 kg (3.3–3.7 lb), both under 8 weeks
Ephedra with caffeine	31	10	5 found extra loss of 0.3–4.9 kg (0.7–10.8 lb)
Conjugated linoleic acid (CLA)	31	5	1 found extra loss of 1.5–3.0 kg (3.3–6.6 lb)
Acupuncture	45	2	No significant difference reported
Calcium with vitamin D	22	5	None found a difference
Mind-body therapies (e.g. hypnosis, meditation)	22	2	Weight differences not reported
Garcinia (hydroxycitrate)	15	4	2 found extra loss of 1.3–3.6 kg (2.9–7.9 lb); 2 found none
Chitosan	9	1	2.3 kg (5.1 lb) more over 6 weeks
Chromium	6	3	1 found 1.4 kg (3.1 lb) more over 72 days
Chocolate or cocoa	6	1	No significant change
White kidney bean (Phaseolus)	7	0	No high-quality trials
Pyruvate	7	0	No high-quality trials
Guar gum	5	0	No high-quality trials
Phenylpropylamine (PPA)	5	1	No significant change

Two patterns stand out. First, the products with the most promotion often have the thinnest high-quality evidence. Second, even the best results are a few kilograms, from short trials, and weren't repeated across most studies of the same product.

Several of these products, such as ephedra and PPA, act like stimulants: the review describes PPA as structurally similar to amphetamine and ephedrine. A small extra loss in a short trial says nothing about long-term safety.

Are Weight Loss Supplements Safe?

You can't assume they are. In the US, a 1994 law known as DSHEA (Dietary Supplement Health and Education Act) loosened regulation of the supplement industry. The Batsis review notes that many consumers, and even some health professionals, wrongly believe the FDA tests supplements for safety and effectiveness before sale. It also notes that some products sold as natural or clinically proven have been recalled after reaching the market.

The NIDDK gives practical safety advice that applies here too:

• Tell your doctor about every supplement you take. Some can affect your weight, your ability to lose weight, or how other medicines work.
• Don't mix weight loss products. Don't combine supplements with prescription weight loss medicines unless a professional prescribes it.
• Watch for big promises. Treat claims of weight loss without changing diet or exercise, rapid loss such as 30 pounds in 30 days, or loss from one body part as warning signs.
• Avoid them in pregnancy. Speak to your doctor before taking any weight loss product if you are pregnant, breastfeeding, or have a health condition.

Weight Loss Supplements for Women

Women are a big part of the market, but there's no evidence that any product works better for them. The review cites research showing supplement use is higher among women, younger adults and people on lower incomes: about a third of adults who try to lose weight say they've used one. Many of the trials were also run mainly in women, and the results were still weak. The same safety advice applies to everyone.

Example: What a Best-Case Result Means

Health experts in the US suggest a first goal of losing 5% of body weight over 6 months. For a person weighing 90 kg (198 lb):

• 5% of 90 kg = 4.5 kg (9.9 lb), the first goal.
• The best green tea result in a high-quality trial was 1.7 kg (3.7 lb), which is about 1.9% of 90 kg.

Even at its best, that is under half of the first goal, and it came from a trial lasting less than 8 weeks. For comparison, the NIDDK reports that prescription medicines, used with a lifestyle program, give 3% to 12% extra weight loss over a year.

What Works Better Than Supplements

The approaches with the strongest evidence are less exciting but far more reliable:

• A modest calorie deficit built on healthy eating. Our guide to the calorie deficit to lose weight shows how to set one.
• A structured program with regular support, tracking and realistic goals, run or overseen by qualified health professionals.
• Ignoring shortcuts. Our guide to common weight loss myths explains why quick fixes rarely last.
• Prescription treatment for people who qualify, under medical supervision. Read our guide to weight loss medication.

Limits and When to Get Advice

This guide summarizes one large review plus NIH guidance. It can't cover every product on sale, and new trials may change the picture for individual ingredients. Products also vary in dose and content, so a trial result may not apply to what's in a given bottle.

Speak to a doctor or pharmacist before taking any supplement for weight loss, especially if you take other medicines, are pregnant or breastfeeding, or have a heart, blood pressure, thyroid or mental health condition. Stop the product and get medical advice if you notice any new or worrying symptoms.

Frequently Asked Questions

Are there any weight loss supplements that actually work?

Not in any reliable way, according to the 2021 review. A handful of high-quality trials found small extra losses for products such as green tea, garcinia, chitosan and CLA. But most good trials of the same products found little or nothing, the studies were short, and the authors judged none to have strong, high-quality evidence of benefit.

Does green tea extract help you lose weight?

The evidence is weak. The review found 38 trials of green tea, 16 of them high quality. Only 2 of those 16 showed a significant extra loss, of 1.5 to 1.7 kg (3.3 to 3.7 lb), and both lasted under 8 weeks. That is too small and too short to count on.

Are weight loss supplements checked by the FDA?

Not in the way medicines are. Since 1994, US law has regulated supplements far more lightly than drugs. The Batsis review points out that many people wrongly believe the FDA reviews supplements for safety and effectiveness before they're sold. Some products have been recalled after going on the market.

Should I take a supplement alongside weight loss medicine?

Only if your prescriber agrees. The NIDDK advises discussing every supplement, vitamin and herbal product you take before starting a weight loss medicine. It also advises against combining weight loss medicines with other weight loss products unless a health care professional prescribes the combination.

To set a realistic daily target instead, use the calorie goal calculator.