Today’s children eat about 350 calories a day more than did kids in the 1970s, the equivalent of a small serving of french fries and a nondiet soda. Grown-ups eat about 500 calories more–about a hamburger’s worth. You could cut those calories by exercising more, of course, but that would require 150 minutes more of walking each day for a child and 110 minutes for adults. Not too realistic.