How much, how long person is overweight may decide diabetes risk

Being obese might up the chance of developing Type 2 diabetes, but the true risk factors may lie in how much overweight someone is and how long they’ve been that way.

Much like figuring how numbers of cigarettes smoked and years of smoking relate to lung cancer risk, researchers set out to see how degree and length of obesity factored into the risk of getting Type 2 diabetes. They looked at data on 8,157 teens and young adults who were 14 to 21 years old at the start of a national study. Participants self-reported their height and weight and diabetes condition from 1981 to 2006.

Excess BMI (body mass index)-years (which researchers likened to smoking-pack years) were calculated by determining to what degree people were over a certain body mass index, and for how long. A BMI of 25, considered overweight, was used as a reference.

After 25 years, 337 people in the study developed diabetes. Researchers found that as time went on, average excess BMI-years increased with age and that more excess BMI-years were linked with a higher risk of diabetes. They gave an example: White 40-year-old men with 200 cumulative excess BMI-years have 2.94-times greater odds of developing diabetes than similar men who have only 100 excess BMI-years.

Race may play a role as well: among those who carried the similar amount of extra weight over the same amount of time, blacks and Hispanics had a greater risk of diabetes.

“We know that, due to the childhood obesity epidemic, younger generations of Americans are becoming heavier much earlier in life, and are carrying the extra weight for longer periods over their lifetimes,” said lead author Dr. Joyce Lee of Mott Children’s Hospital in a news release. “When you add the findings from this study, rates of diabetes in the United States may rise even higher than previously predicted.”

Public health programs about diabetes prevention, the study authors noted, should focus on a younger, ethnic population to stem the tide of the disease. “The tripling of obesity rates for US children during the last 30 to 40 years,” they wrote in the study, “implies that younger generations of individuals are carrying a longer duration of obesity over their lifetime.”

The study was released online Tuesday in the journal Archives of Pediatrics & Adolescent Medicine.