With respect to both physical activity and nutrition, lifestyles of most young Americans have changed dramatically over time. Decades ago, young people often walked miles to attend school, visit friends, or even see a doctor. There was no television to watch, and no Internet to provide hours of visiting without leaving the house. Rather than choosing from an array of pre-packaged and highly processed foods, families tended to cook at home and spent time enjoying meals together. One of the unfortunate results of such lifestyle changes is a sharp rise in obesity, now being identified in a...