Diabetes risk increases with duration of obesity

Research has long shown that obesity might increase an individual's risk of developing type 2 diabetes. But a new study encourages health professionals to assess how overweight the individual is and how long he or she has been obese to get a more accurate idea of the person's diabetes risk.

Authors of the study, published online Sept. 5 in the Archives of Pediatrics and Adolescent Medicine, compared the relationship between excess weight and developing type 2 diabetes with the link between smoking and the risk of lung cancer.

"The amount of excess weight that you carry, and the number of years for which you carry it, dramatically increases your risk of diabetes," said lead study author Joyce M. Lee, MD, MPH, assistant professor in the division of pediatric endocrinology at the University of Michigan Health System.

Dr. Lee recommends that physicians, particularly pediatricians and family physicians, help their young, overweight patients shed pounds to prevent them from becoming obese and developing type 2 diabetes.

Diabetes has been rising steadily in the United States since 1980, when 5.6 million people were diagnosed with the disease, according to the Centers for Disease Control and Prevention. That figure more than tripled by 2009, swelling to about 19.7 million Americans. About 151,000 of those cases have been diagnosed in patients younger than 20.

For the Archives study, researchers assessed data on 8,157 individuals ages 14 to 21 at the start of the National Longitudinal Survey of Youth 1979. They examined participants' self-reported height, weight and diabetes status from 1981 through 2006.

They found that by 2006, 4.2% were obese and 4.1% had developed diabetes. The mean age of diabetes onset was 37.2 years (link).

Researchers also calculated excess BMI-years for the participants. An excess BMI-year measures how much an individual's BMI exceeds 25 (or the 85th percentile for adolescents) and for how long the person was overweight. A BMI greater than 25 is considered overweight. Individuals with a BMI greater than 30 are defined as obese.

The study authors found that higher excess-BMI years were associated with a greater risk of diabetes. For example, a 40-year-old white man with 200 cumulative excess BMI-years had 2.94 times greater odds of developing diabetes compared with a man of the same age and race with 100 excess BMI-years.

Race also seemed to play a role in diabetes risk. The study shows that among individuals who had a similar weight during the same time period, black and Hispanic people were more likely to develop diabetes than whites.

"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," Dr. Lee said.

The study authors recommend that public health officials consider targeting diabetes interventions toward younger, nonwhite individuals to prevent further acceleration of the nation's diabetes rate.