The discovery suggests diets containing the substance, resveratrol, may help combat obesity.
Scientists gave mice amounts of resveratrol equivalent to people consuming 12oz of fruit per day.
They found that despite a high-fat diet, the mice gained 40% less weight than animals not fed it.
The research showed that the mice were able to change their excess white fat to active ‘brown fat’, which burns up calories.
Other ‘polyphenol’ chemicals in fruit may have a similar effect, the scientists believe.
Lead researcher Professor Min Du, from Washington State University, US, said: “Polyphenols convert white fat into beige fat, which burns lipids off as heat, helping to keep the body in balance and prevent obesity.”
Blueberries, strawberries, raspberries, grapes and apples are especially rich in polyphenols.
Red wines such as merlot and cabinet sauvignon are known to contain resveratrol, but at a fraction of the levels found in grapes, Prof Du pointed out.