Although the causes involve a complex interaction of genetic, biological, behavioral, and environmental factors (as this article explains), most cases likely involve too little activity and too much energy intake, particularly added sugars. It is important to note that both diet and activity play a role, and both a targets for prevention and treatment. The same is true for adults, too.
Obesity among children, both young kids and teenagers, is associated with serious health, social, and psychological problems. In fact, obese children, especially those who are inactive, tend to develop “adult” diseases including high blood pressure and diabetes.
And while we know that obesity and inactivity in kids is a problem, I don’t think we realize how bad it is now or will be in the future. That’s because no one has any idea what will happen to an obese 12-year old who develops type 2 diabetes. Adults who become diabetic are at higher risk for an early heart attack; does this mean that a 12-year old will be on the fast track toward a heart attack at age 30?
We don’t know. But I think we are going to find out. Unfortunately, it’s as though we are experimenting with a generation of children to find out.