The American College Health Association estimates that three out of every 10 college students are overweight or obese. Both terms denote ranges of weight that are greater than what is considered healthy for a given height and have been shown to increase the likelihood of diseases. Over the past two decades, the number of American children who are overweight has ballooned. According to the federal Centers for Disease Control and Prevention, the proportion of 12- to 19-year-olds who are overweight has risen from 5 percent to 17.4 percent. College officials are certainly aware that obesity is unhealthy, but institutions have been slow to calculate what their cost will be if students' sedentary habits and poor diets continue to harm their health. Nationally, the obesity epidemic, as it has been called by the U.S. surgeon general, cost an estimated $78.5-billion in medical expenditures in 2000 (the most recent figure available from the federal government), half of which are paid by Medicaid and Medicare. Campus health experts predict that some colleges will have to increase health-services staffing to handle an influx of students with chronic diseases related to obesity. And many believe that colleges should play a part in helping students avoid or overcome being overweight.