[Smaug123]

I'm not expressing an opinion about the causes of the current obesity problem, but your comment had the opposite effect on me than the effect you wanted.

"A quarter of the entire US population didn't suddenly catch a disease and become obese."

Why not? When you put it that way, it strikes me as pretty implausible that 'a quarter of the entire US population suddenly became lazy and started stuffing their faces for no good reason'. Epidemics have happened frequently before; bouts of mass overeating are historically rare.

[bonzini]

It happens a fraction of a percent at a time. Let a population increase their caloric intake by 0.2% a year, while their lives get more and more sedentary, and you will get an obesity epidemic in less than 30 years.

[raquo]

"Unrestricted junk food marketing + 100% sedentary lifestyle between sitting in the office, driving, and watching TV" explains mass obesity trends better than anything else, no pandemic needed.

[hueving]

>Why not?

Because it's obviously not contagious (diseases don't honor human defined borders). It's the culture of junk food and giant meals.