People who are both obese and have diabetes are highly likely to develop heart disease during their lifetime, a new study shows.

Researchers found that of more than 3,400 adults in a long-running U.S. heart study, women who were obese and diabetic had a nearly 80 percent chance of developing heart disease at some point. For their male counterparts, that figure was nearly 90 percent.

Lifetime risk was based on the likelihood that a 50-year-old would develop heart disease in the next 30 years.

Obesity and diabetes commonly go hand-in-hand. The new findings, published in the journal Diabetes Care, show that diabetes on its own significantly raises the lifetime risk of heart disease, and that obesity worsens the situation.

Dr. Caroline S. Fox of the National Heart, Lung and Blood Institute in Bethesda, Maryland, and her colleagues the lifetime heart disease risk of normal-weight women who did not have diabetes was 34 percent. The risk for normal-weight women with diabetes was 55 percent.

Among obese women, those who did not have diabetes had a 47 percent chance of developing heart disease, while the risk for those with diabetes was 79 percent.

The pattern was similar for men, with a lifetime heart disease risk of 49 percent among normal-weight, non-diabetic men, and a 77 percent risk for normal-weight men with diabetes. Obese men without diabetes had a 67 percent lifetime heart disease risk, while the risk for obese diabetic men was 87 percent.

The number of Americans with diabetes is expected to rise to 48.3 million by 2050, the researchers note, and heart disease due to diabetes appears to already be on the rise.

“This trend may continue to worsen if current trajectories do not change,” they warn.

SOURCE: Diabetes Care, August 2008.