Reuters news reported recently on a new study from the journal Cell that explores a contributor to the obesity epidemic.
The study's authors suggest that calorie overload (eating too much at one time) may activate a usually dormant immune system pathway in the brain, causing a chemical imbalance with far reaching effects in the body. This might be part of the reason that weight gain causes such a variety of health problems.
File this under "science can't keep up with culture". We're still figuring out how the body reacts to the toxic nutrition environment produced by our consumer culture. While it's a national tragedy that simply eating what's available - in school or in the US - is a one-way ticket to weight problems, more people are taking charge of their own health, eating more consicously and finding the balance of what and how much to eat that works for them. In today's world, it's the only way to be healthy.