Over the last 50 years American food has become far more calorically dense. Sugar is in everything we eat. When a food is made fat-free they load it with sugar.

Over the last 50 years American food has become far more calorically dense. Sugar is in everything we eat. When a food is made fat-free they load it with sugar. Add to that the car-dependent nature of our infrastructure, the sedentary nature of most jobs worth doing (because money), and you end up exactly where we are. Everyone is gaining weight. Sure it's still calories in and calories out but that is the mechanism you have to look at the whole system.