Obese children are 53 times more likely to have insulin resistance, a syndrome that often precedes development of so-called "adult-onset" Type II diabetes, according to a study by the University of North Carolina at Chapel Hill.
Type II diabetes, which affects an estimated 15 million Americans, typically appears in middle age and is closely linked to obesity. The other less-common form of diabetes, Type I, is an inherited condition in which the body fails to produce enough insulin. Both conditions are potentially deadly and are a leading cause of blindness and amputation.
The study sends a strong signal that the surging incidence of obesity among American children could put many on the fast track for developing Type II diabetes by adolescence or early adulthood, said JoAnne Harrell, a professor of nursing at the university who headed the trial.
"Overall, less than 1 percent of American children now have diabetes. But that could change if we continue to produce obese children," said Harrell, who estimated their obesity rate has doubled in the past decade.
The study of 688 rural children between age 11 and 14 examined a triad of heart disease risk factors that together are considered hallmarks of insulin resistance, a condition also known as multiple metabolic syndrome (MMS).
Insulin is a naturally occurring hormone that removes excess blood sugar, or glucose, from the bloodstream. As people become obese, the body has to crank out ever-higher amounts of the hormone to keep glucose levels under control.
But the overworked insulin eventually loses its ability to do its job, becoming "resistant," and allows glucose to get the upper hand to unhealthy levels that constitute diabetes.
The classic risk factors for insulin resistance which Harrell studied are high insulin levels, high blood pressure and either elevated levels of blood fats known as triglycerides or low levels of the "good" HDL (high density lipoprotein) form of cholesterol that protects against heart disease.
Children with only one of the risk factors were two to six times more likely to be obese, while those with two risk factors were eight to 14 times as likely.
"Kids who were obese were 53 times more likely to have insulin resistance (having all three risk factors) as those who weren't obese. That was totally surprising to me. In fact, it was seven times the rate I would have expected," she said in an interview during the annual scientific sessions of the American Heart Association being held here.
Harrell said she looked at a variety of other factors in the children to see if they were related to insulin resistance, including family health histories, race, gender, puberty level, eating habits and physical activity.
"And the only consistent predictor was obesity. It was absolutely the biggest factor. It didn't matter how the children got obese, whether it was through overeating or inactivity. The key correlation was just being obese," Harrell said.
Insulin resistance is typically present but unknown for about a decade before Type II diabetes is diagnosed. That leads Harrell to predict a wave of obese American children could be confronting the dangerous disease while still in the bloom of youth.
The researcher said she examined the diets of the children in the study and found that they had turned the recommended food pyramid upside down.
"Sweets and fats are supposed to be at the peak of the pyramid, only to be used sparingly. But in the children I studied, they were the base of the pyramid, with an average of nine servings a day," Harrell said.
She theorized many children were also growing fat because of sedentary activities like channel-and Internet surfing and elimination of physical education classes in school.
"Plus, most families now have two working parents who don't have as much time to go out and get active with the kids. Nevertheless, we have to stop the epidemic of obesity in our youth. Otherwise it could be followed by an epidemic of Type II diabetes."