Slim people could be unhealthier than overweight

New research has found that slim people could be unhealthier than overweight people due to a so-called ‘lean gene’.

Scientists behind the research are concerned that the gene, known as IRS1, could fool thin people into thinking that they are healthy and increase their risk of heart disease and type 2 diabetes. They have issued advice that all people, overweight or slim, should follow a healthy lifestyle to avoid the risk of developing such diseases.

Professor Douglas Kiel, from Harvard Medical School in Boston, US, said: “We've uncovered a truly fascinating genetic story and, when we found the effect of this gene, we were very intrigued by the unexpected finding.

“People, particularly men, with a specific form of the gene are both more likely to have lower percent body fat, but also to develop heart disease and type 2 diabetes. In simple terms, it is not only overweight individuals who can be predisposed (to) these metabolic diseases.”

Dr Ruth Loos, of the Medical Research Council’s Epidemiology Unit, explained: “What we’ve discovered is that certain genetic variants keep you lean by reducing how much fat you store under your skin.

“We don’t know for sure, but we can speculate that these individuals are then more predisposed to store fat elsewhere, such as in the liver and in muscle.”

Despite being invisible from the outside, storing fat around the organs is more dangerous than storing it under the skin and is more likely to lead to disease.

Despite the findings, scientists were keen to stress that being overweight is bad for your health.