Carrying extra weight around your middle could mean more than just too-tight pants: You may have a higher risk of heart disease and type 2 diabetes, according to a new study of more than 400,000 people. The authors say that their findings provide the strongest evidence yet that belly fat is directly linked to the development of chronic disease.
Obesity is a well-known risk factor for both heart disease and diabetes. But for any given body mass index (which is calculated using height and weight), distribution of body fat can vary substantially: Some people pack more fat around their hips, for example, and others around their stomachs.
Studies have suggested that people with excess belly fat—aka visceral fat—are more likely to have chronic health problems and die prematurely. “But it wasn’t clear if that was due to the abdominal fat itself, or the fact that people with abdominal fat also tend to have other unhealthy behaviors, like smoking or not exercising,” says lead author Connor Emdin, PhD, a researcher at the Broad Institute of MIT and Harvard.
Since body shape is partially genetic, Emdin and his colleagues wanted to see if they could trace these increased disease risks all the way back to people’s DNA. This could help rule out overlapping effects of lifestyle habits, he says, and show whether abdominal obesity is a risk factor all on its own.
To investigate, the researchers analyzed genomic data and medical records from more than 400,000 people. They found that people who carried combinations of genes that predisposed them to higher waist-to-hip ratios (a measure of abdominal obesity) were 77% more likely to have diabetes, and 46% more likely to have coronary heart disease, than those who weren’t predisposed. They were also more likely to have risk factors for these conditions, such as high cholesterol, high blood pressure, and high blood glucose levels.
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Looking solely at people’s genetic risk—and not at their actual waist-to-hip ratio, which could also be influenced by unhealthy behaviors—helped the researchers conclude, with greater certainty than ever before, that belly fat really does contribute to heart disease and diabetes.
That doesn’t mean people with certain genes are doomed. “The amount of fat that you store around your stomach is influenced by genetics, but it’s also strongly influenced by exercise and diet,” Emdin says. “If you don’t exercise and you don’t eat healthy, you’re going to have a lot more fat around your abdomen.”
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In that sense, Emdin says, the study highlights the importance of a healthy lifestyle—no matter what your genetic background. “The message here is that if you want to reduce your health risks, you should minimize the fat you store around your abdomen,” he says.