Austrian researchers have discovered a possible genetic explanation for why about a quarter of obese people are "metabolically healthy"—meaning they don't have the risk factors for type 2 diabetes.
In their mice study, published in the journal Cell, the researchers were able to determine that high levels of a molecule called HO-1 was linked to poor metabolic health and a higher risk for diabetes in people who are obese. If that molecule is blocked, as they suggest it might be in people who don't have those risks, it could reverse those consequences. Though the researchers' study is very specified to one molecule, it brings into question once again the larger debate about whether there really is such a thing as healthy obesity.
For the last couple of years, there's been back and forth within the medical community on the topic. The scientific concept of healthy obesity stems from recent studies that show some overweight or obese people are just as healthy as normal-weight individuals since they have normal blood pressure, they are not diabetic and they good cholesterol levels. There has even been one study that found overweight individuals lived longer than healthy-weight people. On the other hand, researchers at Mount Sinai Hospital in Toronto reviewed studies dating back to the 1950s and came to the conclusion that people cannot be both overweight and healthy. Another recent study published in the Journal of the American College of Cardiology looked at 14,828 metabolically healthy Korean adults came to the same conclusion.
“Obese individuals who are considered healthy because they don’t currently have heart-disease risk factors should not be assumed healthy by their doctors,” study author Dr. Yoosoo Chang in a statement.
But what is often overlooked in the debate is that while genes influence the body's responses to various environments, they do not guarantee a person will be thin or overweight. "Most obesity...probably results from complex interactions among multiple genes and environmental factors that remain poorly understood," states the Centers for Disease Control and Prevention's explainer on obesity and genetics. And indeed, many things can play a part in whether a persons' genes express themselves or not.
"In genetics, there are exceptions to almost every rule," says Joy Larsen Haidle, the president-elect of the National Society of Genetic Counselors. "Studies have been done looking at identical twins with a predisposition to obesity. Not surprisingly, the twins who were physically active had less issues with body mass than the twins who were more sedentary."
So yes, perhaps the HO-1 molecule has some implications but in the grand scheme of influence, it's just a drop in the pond. What matters more is that efforts to lower the obesity rate in the U.S. take a comprehensive approach.