The risk of developing type 2 diabetes by age 20 was 12 times as high in severely obese American Indian children aged 5-9 years of age as in normal-weight youth in that age range, a new study has revealed.

Obesity is a serious health problem among youth, especially in populations at high risk of developing type 2 diabetes. Previous studies of obesity in youth have reported a strong relationship between body mass index (BMI) and then the subsequent incidence of type 2 diabetes in adults and adolescents. However, prior studies have not assessed the long-term risk in youths with extremely high BMIs.

This longitudinal study, presented at the American Diabetes Association’s 77th Scientific Sessions, examined the risk of diabetes and other metabolic abnormalities in obese and severely obese American Indian youths from the southwestern US, a population with a high risk of developing type 2 diabetes.

The incidence of type 2 diabetes was computed in 2,728 children without diabetes aged 5-9 years, and a partially overlapping group of 4,317 youths aged 10-17 years. They were followed up to age 45 or until the onset of type 2 diabetes. Age-sex specific BMI percentiles were defined by the 2000 US Centers for Disease Control and Prevention (CDC) growth charts. The CDC defines obesity as being at or above a cut-point specified as the 95th BMI percentile.

Type 2 diabetes incidence rates increased in direct proportion with severity of obesity. Compared with 5-9-year old non-obese children with BMIs in the middle of the BMI distribution, children of the same age with BMIs at least 40% above the cut-point defining obesity had 12 times the incidence rates of type 2 diabetes by age 20 years and three times the incidence rates of type 2 diabetes by age 45 years. BMI had similar effects on type 2 diabetes incidence in those 10-17 years old at baseline.

Study author Madhumita Sinha, staff clinician at the Diabetes Epidemiology and Clinical Research Section of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) at the National Institutes of Health (NIH) in Phoenix, Ariz, said: “We had previously found BMI in youth to be a strong predictor of type 2 diabetes, but we had not examined diabetes incidence rates in those with the severe degree of obesity that is prevalent today. We did not know if diabetes incidence rates among the obese plateaued among those with extremely high BMI. This study clearly shows that the risk of developing type 2 diabetes is associated with BMI, especially at very high extremes.

“Parents and health care providers should be aware of the future diabetes risk associated with obesity in youth, especially as more severe degrees of obesity become more prevalent,” explained Sinha. “Results of our analysis emphasize the importance of developing effective means of preventing or treating obesity in youth, and additional risk factors for type 2 diabetes in youth should be explored for their interactions with severe obesity.”