The biggest risk to children's health is one which happens incrementally as students move through the school grades and into adulthood. Obesity has reached such proportions that today's children could end up living two to five years less than they might otherwise, according to a 2005 study in the New England Journal of Medicine. According to the federal Centers for Disease Control and Prevention (CDC), the percentage of overweight children age 6 to 11 more than doubled in the past two decades, rising from 7 percent in 1980 to 16 percent in 2002. Among adolescents age 12 to 19, the share more than tripled, going from 5 percent to 16 percent over the same period.