A compound found in berries, grapes and some fruits can convert excess flab into calorie burning brown fat, says a new study.

Mice fed on resveratrol equivalent to humans consuming 12 ounces of fruit per day showed that despite a high fat diet, the mice gained 40% less weight than the control animals.

The mice achieved this by changing excess white fat to "brown" or "beige" fat which burns up calories. An enzyme called AMPK stimulates this transition.

Lead researcher Min Du, from Washington State University, US, said: "Polyphenols in fruit, including resveratrol, increase gene expression that enhances the oxidation of dietary fats so the body won't be overloaded.

"They convert white fat into beige fat which burns lipids (fats) off as heat, helping to keep the body in balance and prevent obesity and metabolic dysfunction."

Types of fat cells
White fat cells store energy and brown fat cells serve as fat-burning, heat generating machinery.

Beige fat, which is in between white and brown fat is generated from white fat in a process called "browning."

Resveratrol can enhance this conversion of white fat to beige and partially prevent obesity.

Red wines such as merlot or cabinet sauvignon are also known to contain resveratrol, but much of it is filtered out during wine production.

Du said resveratrol is only one of the polyphenolic compounds found in fruit that provides beneficial health effects. "In reality, it's the total polyphenolic content that is more important," he said. "We think you can increase your total intake of polyphenol compounds by directly increasing fruit consumption."

Blueberries, strawberries, raspberries, grapes and apples are especially rich in such compounds.

White fat is protective when it is healthy but an excess leads to imbalance and disease.
"The current theory is that when we eat excessively, the extra lipids are stored in white fat. With obesity, the fat cells enlarge to a point where they're saturated and can't uptake more lipids," Du said. "As the fat cells become overloaded and die, they release toxins and cause inflammation leading to health problems like insulin resistance and diabetes."

The findings are reported in the International Journal of Obesity.

Benefits of resveratrol
The antioxidant resveratrol has been shown in studies to protect the heart against cardiovascular diseases by inhibiting inflammatory factors, besides helping to improve memory by its effect on the hippocampus area of the brain.

Antioxidants generally play a beneficial role in the health of cells by reducing oxidation and controlling free radicals which damage cells leading to cancer, immune diseases and heart problems.

More than 2.1 billion people in the world are overweight or obese, with the figure set to rise to include nearly half of the population by 2030. A recent report had shown that the burden of obesity in the UK could beat the total costs of war and terrorism.