SO....what do you think cause such an increase in the prevalence of obesity over the last 20 years?
In the broadest sense, technological progess has created the obesity epedemic. You can sit around and nitpick different food types and different industries, but the plain fact is that humans evolved as hunter/gatherers and now we no longer engage in these activities. Today's society allows people to sit around and eat....and survive. Every step along our societal evolution was a step toward more security, more food, and less work. Now our machines do most of the work and will continue to do so into the future. Most exercise is for liesure activities. Nobody wants to go back to the days of survival in the wild and no one wants to be told what they can and cannot eat or how much. And therefore, like I mentioned earlier, the most optimal solution would be to create cheap, very tasty food, that is packed with nutrition, and doesn't have many calories...a healthy twinkie perhaps.