About two-thirds of American adults and almost one-fifth of those ages 6 to 19 are overweight or obese, according to the Centers for Disease Control and Prevention (CDC). The percentage of young people who are overweight has more than tripled since 1980, the agency reports. The International Obesity Taskforce warns that 10 percent of school-age children worldwide are overweight or obese, with rates continuing to soar. Health experts are concerned because obesity is the leading controllable risk factor for type 2 diabetes.

Obesity carries a fivefold greater risk for developing type 2 diabetes. But the risk is not confined to obesity, which is a body mass index (BMI) of 30 or greater. Being overweight (defined as a BMI of 25 to 29) also increases the risk of diabetes.

The CDC estimates that one out of three children born in the year 2000 will develop diabetes sometime during their lifetime. The estimate is higher for racial minorities.

Unless this trend is reversed, these numbers will increase by 165 percent by 2050, according to the agency.

Obesity may also lead to a phenomenon called double diabetes, in which children with type 1 diabetes develop insulin resistance. Obesity has grown more prevalent in people with type 1 diabetes along with the general population. Excess fat makes it harder to use insulin. Excess weight may also cause the pancreas to deteriorate. Recent research suggests that obesity might cause an earlier onset of type 1 diabetes.

Childhood diabetes is a particular concern because the longer a person has diabetes, the greater the risk of serious complications. This can include damage to the eyes, nerves, heart, blood vessels, kidneys and skin. Some physicians are seeing teenagers who have already developed what were once considered long-term complications of type 2 diabetes.

The CDC reviewed the discharge records of hospitals nationwide from 1979 to 1999 among children ranging ages 6 to 17 and analyzed the results for all obesity-related illnesses. The researchers found that the incidence of:

• Diabetes had nearly doubled
• Obesity and gallbladder disease tripled
• Sleep apnea increased five-fold

The CDC found that these illnesses in children combined to create hospital costs that have tripled as a direct result of childhood obesity. In addition to the high cost of health care for these children, there is an even greater cost in human life. For the general population, the National Institutes of Health estimates that obese people have a 50 to 100 percent increased risk of death compared to people of normal weight.