Body Type May Influence Diabetes, Heart Disease Risks

Genetic variants linked to body shape may influence the risk of developing certain diseases, such as diabetes and heart disease, according to a new study published by JAMA.

The study authors found that individuals who have their weight deposited around the abdomen, rather than in the hips and thighs, have an increased risk for type 2 diabetes, coronary heart disease, and multiple cardiovascular risk factors.

"People vary in their distribution of body fat -- some put fat in their belly, which we call abdominal adiposity, and some in their hips and thighs," said senior study author Sekar Kathiresan, MD. "Abdominal adiposity has been correlated with cardiometabolic disease, but whether it actually has a role in causing those conditions was unknown. We tested whether genetic predisposition to abdominal adiposity was associated with the risk for type 2 diabetes and coronary heart disease and found that the answer was a firm 'yes'."

Although several observational studies have suggested that type 2 diabetes and heart disease is more prevalent among those with abdominal adiposity, lifestyle factors were not factored in. Diet, smoking, and physical inactivity are all known to cause an increase in diabetes and heart disease. Additionally, individuals in the initial stages of heart disease may develop abdominal adiposity due to a diminished ability to be active.

The new study was specifically designed to determine whether abdominal adiposity could increase cardiometabolic risk, independent of other risk factors.

The investigators measured whether gene variants cause an increased risk of diabetes and heart disease through mendelian randomization. To do so, they gathered previously established data regarding genes that influence waist-to-hip ratio to develop a genetic risk score for each patient.

Then, the investigators applied the genetic risk score to more than 400,000 patients included in other studies and from the UK Biobank to determine any link between gene variants and abdominal adiposity and cardiometabolic disease, according to the study.

Their findings suggested that genetic predisposition to abdominal adiposity is linked to increased risk of diabetes and heart disease. Patients were also observed to have increased blood lipids, blood glucose, and systolic blood pressure.

The investigators also did not find a link between genetic risk score and lifestyle. Further testing showed that abdominal adiposity was the sole factor in increasing cardiometabolic risks, according to the study.

"These results illustrate the power of using genetics as a method of determining the effects of a characteristic like abdominal adiposity on cardiometabolic outcomes," said lead author Connor Emdin, DPhil. "The lack of association between the body type genetic risk score and confounding factors such as diet and smoking provides strong evidence that abdominal adiposity itself contributes to causing type 2 diabetes and heart disease."

The authors noted that additional studies should be conducted to confirm their findings. These results could better target individuals who are at risk of developing cardiometabolic disease in order to implement prevention strategies focused on reducing the risk associated with modifiable factors, such as diet or exercise.

"Not only do these results allow us to use body shape as a marker for increased cardiometabolic risk, they also suggest that developing drugs that modify fat distribution may help prevent these diseases,” Dr Emdin said. “Future research also could identify individual genes that could be targeted to improve body fat distribution to reduce these risks."