GCA Clinical Evidence
GCA (Green Coffee Chlorogenic Acid Extract)
Diabetes, Metabolic Syndrome and Obesity
Vinson JA, BR Burnham, MV Nagendran. Randomized, double-blind, placebo-controlled, linear dose crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjects. 2012; 5:21–7.
Can green coffee bean extract help overweight subjects lose weight?
Green coffee extract (GCA) contains chlorogenic acids, which have a known effect on glucose and fat metabolism.
Human clinical intervention trial
Randomized, double-blind, placebo-controlled crossover study. Subjects took a high dose, a low dose, or a placebo for 6 weeks each, with 2-week washout periods in between. Researchers measured their body weight, body mass index, body fat percentage, heart rate, and blood pressure. There were no dietary changes.
1,050 mg or 750 mg for 6 weeks each
16 overweight adults
Subjects experienced significant weight loss in both GCA dosage groups (high dose: 2.04 ± 2.20 kg, low dose: 1.54 ± 1.74 kg) but not in the placebo group. In both GCA dosage groups, participants also saw significant reductions in BMI (high dose: 0.74 ± 0.80 kg/m2, low dose: 0.58 ± 0.66 kg/m2), while subjects in the placebo group did not.
“The results suggest that GCA may be an effective nutraceutical in reducing weight in preobese adults, and may be an inexpensive means of preventing obesity in overweight adults."
Gastroenterology Research and Practice
Onakpoya I, R Terry, E Ernst. The use of green coffee extract as a weight loss supplement: a systematic review and meta-analysis of randomized clinical trials. 20
Is green coffee extract an effective weight loss supplement?
Research into green coffee extract is in the beginning phases. What has been found so far?
Five studies of green coffee extract were considered, all of which were found to be at risk of bias. However, data from 3 of higher methodological quality were pooled and analyzed. Researchers found a significant but moderate weight loss compared with placebo (2.47 kg).
“It is concluded that the results from these trials are promising, but the studies are all of poor methodological quality. More rigorous trials are needed to assess the usefulness of GCE as a weight loss tool.”
Mechanism of Action
Chlorogenic acids in GCA lower levels of triglycerides in the liver. They may also block glucose absorption by inhibiting amylase, an enzyme that breaks down carbohydrates. Caffeine also suppresses fat absorption. Other phenolic compounds in coffee enhance the activity of CTP, an enzyme involved in fatty acid metabolism in the liver. GCA has been shown to inhibit pancreatic lipase in vitro and lipoprotein lipase in humans, leading to decreased absorption of fats. Coffee polyphenols also increase metabolism and reduce fat accumulation by downregulating proteins that govern these functions.