Being slim may not always mean a lower risk of heart disease and diabetes, scientists said after they identified a gene linked both to having a lean body and to a higher risk of metabolic diseases, according to an article published by Reuters.com on June 26.

While a so-called "lean gene" was linked to having less body fat, it was also linked to an increased risk of heart disease and type 2 diabetes, researchers from Britain's Medical Research Council Epidemiology Unit said.

Ruth Loos, whose study was published in Nature Genetics journal, said her team examined the genetic code of more than 75,000 people to look for the genes that determine body fat percentage, and found strong evidence that a gene called IRS1 is linked with having less body fat.

When they investigated further, they found IRS1 also leads to having unhealthy levels of cholesterol and glucose in blood - key markers for so-called metabolic diseases like heart disease and diabetes - illnesses normally associated with being overweight.

Loos said the findings suggest that people with the IRS1 gene are less able to store subcutaneous fat, and may therefore store fat in other parts of the body where it might pose more risk to organ function.

However, she added that the study results did not change the general message for most people. "People who are lean are generally healthier than people who are overweight or obese," the article quoted her as saying.

Heart disease is the world's biggest killer, claiming 17.1 million lives a year, according to the World Health Organization. Experts say a global epidemic of obesity is threatening to cause a wave of heart disease and type 2 diabetes.