Green Coffee Weight Loss: What the Research Says

In short: Green coffee weight loss claims took off in 2012, but the study that made headlines was later retracted. Pooled results from newer trials suggest green coffee bean extract may help people lose about 1 kg (2–3 lb) more than a placebo over a few months, and the studies behind that number are small and mixed in quality. It’s not a shortcut, and the caffeine in it has its own side effects.

Green coffee beans are simply coffee beans that haven’t been roasted yet. Interest in green coffee weight loss supplements comes down to one group of plant compounds: chlorogenic acids, a family of natural antioxidants (compounds that help limit cell damage) found in coffee. Raw beans are packed with them, but roasting destroys most of them. In one lab analysis, green beans contained about 34–42 mg of chlorogenic acids per gram, while roasted beans had only about 2–7 mg per gram, and the darker the roast, the lower the level [1]. Green coffee extract is made from the unroasted beans, so it keeps far more chlorogenic acid than your morning cup [2].

Green coffee vs. roasted coffee

Roasting changes more than flavor. An older lab study compared green and roasted coffee and found green coffee had slightly higher antioxidant activity in a test tube. Interestingly, roasted coffee did better on a second test of how well it protected rat liver cells from damage, so “raw” isn’t automatically “healthier” [3].

Roasting also helps with food safety. Coffee beans can carry small amounts of ochratoxin A, a toxin made by certain molds. In an industry study, roasting and processing cut ochratoxin A levels sharply: the final instant coffee powder kept only about 13% of the amount found in the original green beans [4]. That’s one reason it’s worth choosing green coffee products from makers that test for contaminants.

How green coffee might affect weight

The theory is that chlorogenic acid may slow how quickly the body absorbs sugar from food and may change how fat is stored. Most of the support for this comes from animal research. In one study, mice fed green coffee bean extract for two weeks ended up with lower body weight and less belly (visceral) fat than mice on the same diet without it, and the extract also tended to lower fat in the liver [5]. Results in mice don’t always carry over to people, though, so human trials are what really count.

Green coffee extract also contains some caffeine (more on that under side effects below). Either way, weight change still comes down to your overall energy balance over time (see our guide to energy homeostasis).

What the human studies say about green coffee weight loss

The early review: promising, but weak

The first systematic review (a study that pulls together all the trials on a question) appeared in 2010. Only three small trials met the reviewers’ standards. People taking green coffee extract lost about 2.5 kg (5.4 lb) more than people taking a placebo, but the authors rated all three trials as having a high risk of bias, and the results varied a lot between them. Their conclusion: promising, but more rigorous trials were needed [6].

The famous study that was retracted

The study that made green coffee famous was a tiny 2012 trial in 16 overweight adults. It reported an average weight loss of about 8 kg (17.7 lb) over 22 weeks, and it was widely promoted on TV [7]. In 2014 the authors retracted it, saying the study’s sponsors couldn’t vouch for the validity of the data [8].

That same year, the U.S. Federal Trade Commission (FTC) charged the company that paid for the trial with using a “seriously flawed” study to market its product. According to the FTC, the lead investigator in India changed participants’ weights and other measurements, changed the length of the trial, and mixed up who took the placebo and who took the extract. The company agreed to pay $3.5 million [9]. So if you’ve seen green coffee headlines promising dramatic results, they were most likely built on this study.

Newer reviews: a small effect at best

Since then, researchers have pooled more trials, and the results are much more modest:

• A 2019 meta-analysis (a study that combines results from many trials) of 16 trials found a small drop in BMI (body mass index, a weight-for-height measure), but no significant change in body weight overall. The effect looked a bit stronger in people who started out overweight, and supplements taken for less than four weeks had no effect [10].
• A 2020 meta-analysis of 15 trials with 897 people found green coffee extract lowered body weight by about 1.2 kg (2.7 lb) on average compared with a control group, with small drops in BMI and waist size. Higher doses of chlorogenic acid didn’t lead to bigger results [11].
• A 2023 “umbrella” review, which combined five earlier meta-analyses, landed in the same place: about 1.2 kg (2.7 lb) of extra weight loss, plus about half a centimeter (less than a quarter of an inch) off the waist [12].

Put simply, if green coffee extract does anything for weight, it’s a small effect. Many of the trials were short, small, run in a single country, or funded by supplement makers. The U.S. National Institutes of Health’s Office of Dietary Supplements sums it up this way: only a few human trials exist, and they were all of poor methodological quality [2].

Other possible benefits: blood pressure

Chlorogenic acid has also been studied for blood pressure. A 2014 review of five trials with 364 people found modest drops of about 4 mmHg in systolic pressure (the top number) and about 3–4 mmHg in diastolic pressure (the bottom number). However, the trials were all done in Asian populations, varied in design, and were funded by companies that make chlorogenic acid products, so the authors called for larger independent trials [13].

Side effects and safety

Green coffee bean extract seems to be well tolerated in studies, but its safety hasn’t been studied rigorously. Reported side effects include headaches and urinary tract infections [2].

The bigger practical issue is caffeine. Green coffee beans naturally contain it, and caffeine is a stimulant that can cause side effects [2]. The FDA says up to 400 mg of caffeine a day (about two to three 12-ounce cups of coffee) isn’t generally linked to harmful effects in most healthy adults. Too much can cause a racing heart, jitters, anxiety, trouble sleeping, an upset stomach, nausea and headaches [14]. If you also drink coffee, tea, energy drinks or take a caffeine-containing pre-workout, check the label so you don’t stack up more caffeine than you realize. People who are pregnant or breastfeeding, sensitive to caffeine, taking medications, or living with heart problems or high blood pressure should talk to their doctor first.

How much do studies use?

Doses vary a lot between products and trials. In the 2023 umbrella review, doses of 600 mg a day or less, taken for more than seven weeks, were the most likely to show a small effect on body weight [12]. Supplement labels differ in how much chlorogenic acid and caffeine they contain, so it’s worth reading the label closely.

The bottom line on green coffee weight loss

Green coffee weight loss claims are much bigger than the evidence. The study that made it famous was retracted, and the best current estimate from pooled trials is an extra 1 kg or so (2–3 lb) over a few months, based on mostly small, lower-quality studies. That’s a similar story to other popular weight loss supplements, such as hydroxycitric acid and calcium. If you decide to try green coffee extract, keep your expectations realistic, count its caffeine toward your daily total, and focus first on the basics that move the needle most: what you eat, how active you are, and how well you sleep.

This article is for general information only and isn’t medical advice. Talk to your doctor or another qualified health professional before starting a new supplement. See our medical disclaimer.

References

1. Moon JK, Yoo HS, Shibamoto T. Role of roasting conditions in the level of chlorogenic acid content in coffee beans: correlation with coffee acidity. Journal of Agricultural and Food Chemistry. 2009;57(12):5365–5369. doi:10.1021/jf900012b
2. Office of Dietary Supplements, National Institutes of Health. Dietary Supplements for Weight Loss: Fact Sheet for Health Professionals (Green coffee bean extract). ods.od.nih.gov
3. Daglia M, Papetti A, Gregotti C, Bertè F, Gazzani G. In vitro antioxidant and ex vivo protective activities of green and roasted coffee. Journal of Agricultural and Food Chemistry. 2000;48(5):1449–1454. doi:10.1021/jf990510g
4. Blanc M, Pittet A, Muñoz-Box R, Viani R. Behavior of ochratoxin A during green coffee roasting and soluble coffee manufacture. Journal of Agricultural and Food Chemistry. 1998;46(2):673–675. doi:10.1021/jf9707703
5. Shimoda H, Seki E, Aitani M. Inhibitory effect of green coffee bean extract on fat accumulation and body weight gain in mice. BMC Complementary and Alternative Medicine. 2006;6:9. doi:10.1186/1472-6882-6-9
6. Onakpoya I, Terry R, Ernst E. The use of green coffee extract as a weight loss supplement: a systematic review and meta-analysis of randomised clinical trials. Gastroenterology Research and Practice. 2011;2011:382852. doi:10.1155/2011/382852
7. Vinson JA, Burnham BR, Nagendran MV. Randomized, double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjects. Diabetes, Metabolic Syndrome and Obesity. 2012;5:21–27. [Retracted] doi:10.2147/DMSO.S27665
8. Retraction notice: Randomized, double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjects. Diabetes, Metabolic Syndrome and Obesity. 2014;7:467. doi:10.2147/DMSO.S75357
9. Federal Trade Commission. Green coffee bean manufacturer settles FTC charges of pushing its product based on results of “seriously flawed” weight loss study. Press release, September 8, 2014. ftc.gov
10. Gorji Z, Varkaneh HK, Talaei S, et al. The effect of green-coffee extract supplementation on obesity: a systematic review and dose-response meta-analysis of randomized controlled trials. Phytomedicine. 2019;63:153018. doi:10.1016/j.phymed.2019.153018
11. Asbaghi O, Sadeghian M, Rahmani S, et al. The effect of green coffee extract supplementation on anthropometric measures in adults: a comprehensive systematic review and dose-response meta-analysis of randomized clinical trials. Complementary Therapies in Medicine. 2020;51:102424. doi:10.1016/j.ctim.2020.102424
12. Yang Z, Shao Z, Ouyang W, et al. The effect of green coffee extract supplementation on obesity indices: critical umbrella review of interventional meta-analyses. Critical Reviews in Food Science and Nutrition. 2024;64(29):10537–10545. doi:10.1080/10408398.2023.2225614
13. Onakpoya IJ, Spencer EA, Thompson MJ, Heneghan CJ. The effect of chlorogenic acid on blood pressure: a systematic review and meta-analysis of randomized clinical trials. Journal of Human Hypertension. 2015;29(2):77–81. doi:10.1038/jhh.2014.46
14. U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine Is Too Much? fda.gov