A trending "miracle" weight-loss product is green coffee bean dietary supplements. Some people swear by them and marketing claims are not modest about the effectiveness.

But do they actually work or is it placebo and/or other changes (exercise, diet) that concerned people adapt?

Science would never criticize coffee. It is rich in healthful, natural, plant-based polyphenol substances and evidence from past studies links coffee drinking to a lower risk of obesity, high blood pressure, type 2 diabetes and other disorders collectively termed the "metabolic syndrome."  Chlorogenic acid (CGA), one coffee polyphenol, is the main ingredient in scores of dietary supplements promoted as weight-loss products.

Yet chlorogenic acid doesn't prevent weight gain in obese laboratory mice fed a high-fat diet when given at higher doses, according to a new paper in Journal of Agricultural and Food Chemistry.

Worse than showing no benefit, CGA was linked to an unhealthy build-up of fat in the liver. 

The report found that mice on a high-fat diet and mice on a high-fat diet plus CGA gained the same amount of weight. The CGA mice, however, were more likely to develop disorders that often lead to type 2 diabetes. They also accumulated fat inside the cells in their livers.

"This study suggests that higher doses of CGA supplementation in a high-fat diet does not protect against features of the metabolic syndrome in diet-induced obese mice," they say.