Jane Galt has this wonderful post pointing out a problem with various woeful laments of the fattening of America.
One of the criticisms of the set point theory is that people used to be thinner. And it is true, there weren't so many obese people around. But we are fooled by old movies into thinking that this means everyone used to be thin.
But look at this randomly selected ninth grade photo...
(Set point theory is the argument that all people have a weight that their body tends towards, because of the structure of their metabolism, or--I've read recently, because of the structure of the cells themselves.)
