Researchers who set out to show how coffee benefits the heart instead ended up demonstrating how it could make people gain weight.
The study from the Western Australian Institute for Medical Research and the University of Western Australia's School of Medicine and Pharmacology looked into a compound found in coffee called Chlorogenic Acid (CGA).
Because studies had previously shown consumption of a chemical other than caffeine in coffee reduced the risk of type-2 diabetes, the researchers focussed on CGAs - which are very rich in coffee.
CGAs were known for their health benefits, including increasing insulin sensitivity, reducing blood pressure, and minimising body fat accumulation, one of the researchers said.
"However, this study proved the opposite in dosages equivalent to five or six cups of coffee per day," Assistant Professor Vance Matthews said.
When the equivalent dose of CGA was fed to lab mice, it affected the way fat was used in the liver, and caused abnormal retention of fat within cells.
The obese mice also had a tendency for a higher degree of glucose intolerance and increased insulin resistance.
Matthews said the health effects depended on the dosage, and moderate amounts of coffee would be fine.
"Up to three to four cups a day still seems to decrease the risk of developing diseases such as cardiovascular disease and type-2 diabetes," he said.
"Everybody knows about the effects of caffeine, but when we're considering our lifestyle choices it's important to remember that compounds such as CGA can have an effect on our health if they're not consumed in moderation."
The study was published in the Journal of Agricultural and Food Chemistry.
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