Researchers from the Medical Research Council project in Cambridge revealed that people who have a specific type of "lean" gene may be at a higher risk of suffering from type II diabetes even though they may look trim and fit.
The researchers found the gene, known as IRS1, which will reduce the amount of fat below the skin but increase the risk of type II diabetes and other heart problems.
The study was published in the journal Nature Genetics and involved researchers from 10 different countries.
Commenting on the finding, lead researcher Dr Ruth Loos said, "People, particularly men, with a specific form of the gene are more likely to be lean and to develop heart disease and type 2 diabetes. In simple terms, it is not only overweight individuals who can be predisposed for these diseases, and lean individuals shouldn't make assumptions that they are healthy based on their appearance."