Volume 346:854-855 March 14, 2002 Number 11

Childhood Obesity and a Diabetes Epidemic

Childhood obesity has reached epidemic proportions; worldwide, approximately 22 million children under five years of age are overweight.1 During the past three decades, the number of overweight children in the Unites States has more than doubled. In 1983, 18.6 percent of preschool children in the United States were defined as overweight, and 8.5 percent were defined as obese; by 2000, 22.0 percent of preschool children were overweight and 10.0 percent were obese.1 Data from the National Longitudinal Survey of Youth indicate that the prevalence of overweight has increased by 21.5 percent among non-Hispanic black children, 21.8 percent among Hispanic children, and 12.3 percent among non-Hispanic white children.2 Similar increases in the prevalence of obesity have been observed worldwide.3 Childhood obesity is the most serious and prevalent nutritional disorder in the United States.

Obesity has a substantial effect on cardiovascular risk. Childhood obesity is directly linked to abnormalities in blood-pressure, lipid, lipoprotein, and insulin levels in adults, as well as to the risk of both coronary artery disease and diabetes.4 Becque and coworkers5 evaluated the incidence of risk factors for coronary heart disease in a group of obese adolescents and documented that 80 percent had elevated systolic blood pressure, diastolic blood pressure, or both. Furthermore, they found that 97 percent had four or more of the following cardiovascular risk factors: elevated serum triglyceride levels (more than 100 mg per deciliter), low levels of high-density lipoprotein cholesterol (below the 10th percentile for age and sex), increased total cholesterol levels (more than 200 mg per deciliter), elevated systolic blood pressure, diastolic blood pressure, or both (above the 90th percentile for age and sex), diminished maximal oxygen consumption (less than 24 ml per kilogram of body weight per minute), and a strong history in the immediate family of coronary heart disease, myocardial infarction, angina pectoris, or high blood pressure.5

Obese children also have a higher prevalence of insulin resistance and type 2 diabetes. As the prevalence of childhood obesity increased between 1982 and 1994, the incidence of type 2 diabetes increased by nearly a factor of 10, according to one report from Cincinnati.6 The authors of that report also observed that in 1996, one third of all new cases of diabetes in children 10 to 19 years of age could be classified as type 2, resulting in an age-specific incidence of 7.2 per 100,000 children per year.6 Among Japanese schoolchildren, the incidence of type 2 diabetes increased from 0.2 to 7.3 per 100,000 children per year between 1976 and 19957 — an increase that was attributed to changing dietary patterns and increasing rates of obesity among these children. In some areas of Japan, type 2 diabetes has now become the dominant form of diabetes in children and adolescents.8

The study by Sinha et al.9 in this issue of the Journal has for the first time determined the prevalence of impaired glucose tolerance in obese children, documenting impaired glucose tolerance in 25 percent of 55 obese children (4 to 10 years of age) and in 21 percent of 112 obese adolescents (11 to 18 years of age). In addition, clinically asymptomatic, or silent, type 2 diabetes was uncovered in 4 of the 112 obese adolescents (4 percent).

Besides documenting the high incidence of impaired glucose tolerance in severely obese children, Sinha and coworkers also demonstrated that insulin resistance and fasting hyperproinsulinemia were the most important predictors of impaired glucose tolerance. Neither the degree of obesity nor a family history of diabetes was a significant risk factor for glucose intolerance. However, Sinha and coworkers studied only children who were markedly obese. All the children they studied had a body-mass index (the weight in kilograms divided by the square of the height in meters) above the 95th percentile for age and sex (a body-mass index of more than 29 for children and more than 35 for adolescents). In contrast, Sinaiko et al.10 have shown that, in adolescents, there is a significant correlation between the body-mass index and the degree of insulin resistance as measured by the hyperinsulinemic–euglycemic clamp technique. In the Sinaiko study, body-mass index ranged from 14 to 42. Since Sinha and coworkers studied a group of severely obese children and adolescents, it is possible that if their study group had included subjects with a broader range of adiposity, other factors might have predicted the presence of impaired glucose tolerance.

Finally, Sinha and coworkers performed a second glucose-tolerance test in several subjects to confirm the diagnosis of impaired glucose tolerance. They also demonstrated, in two of three subjects who were followed for two to five years, that impaired glucose tolerance progressed to frank diabetes.

Epidemiologic evidence from the past 20 years has demonstrated that the increasing incidence of type 2 diabetes in children parallels the increasing prevalence of obesity.11,12 When we consider these epidemiologic data in conjunction with both the current worldwide epidemic of childhood obesity and the evidently high incidence (greater than 20 percent) of impaired glucose tolerance in severely obese children, it appears that there is an emerging pediatric epidemic of type 2 diabetes. If this epidemic cannot be averted, its full public health effect will be felt as affected children become adults and the long-term complications of diabetes develop.

The prevention and treatment of type 2 diabetes present an enormous challenge. The obvious way to prevent an epidemic of obesity-related diabetes would be to emphasize the primary and secondary prevention of obesity. However, despite all our best efforts, prevention of childhood obesity eludes our grasp. Similarly, although it is possible to treat obesity, it is extremely difficult and requires both extensive resources and a very highly motivated child and family. Even with successful weight loss, the rate of relapse is high. I believe that a more effective strategy is to identify those obese children who are at high risk for diabetes and to target them for intensive weight-loss treatment. Given the observations of Sinha and coworkers, oral glucose-tolerance testing appears to be an excellent method for reliably identifying obese children who are at high risk for diabetes.

Albert P. Rocchini, M.D.

University of Michigan

Ann Arbor, MI 48109-0204

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