Individuals with a thin physical appearance take heed: Health is much more than skin deep. A study done at the Medical Research Council in Cambridge, England, discovered that some individuals who appear to have low body fat may actually be at high risk for health problems. The study is published in Nature Genetics (2011; 43, 753–60).

The scientists analyzed the genetic code of more than 75,000 people to single out genes associated with lower body fat percentage. They located a gene—IRS1—that seemed to be linked with lower subcutaneous body fat. However, individuals possessing this gene also had higher levels of blood glucose and cholesterol, as well as visceral body fat. The authors posit that this is evidence that individuals with the specific variation of the gene store fat differently than those without the variation.

“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,” warned the study authors in a press release. “In simple terms, it is not only overweight individuals who can be predisposed for these metabolic diseases, and lean individuals shouldn’t make assumptions that they are healthy based on their appearance.”

The authors added that these findings underscore the importance of engaging in healthy lifestyle activities, regardless of one’s physical appearance.