What factors have contributed to the obesity epidemic in the United States?

I think the primary cause of obesity in the United States is industrially manufactured foodstuffs that are inexpensive and highly palatable. There's easy access to fattening and low nutrition foods that do not cost a great deal for the average consumer. At a budget store I can by bakery goods at you can often get pies and cup cakes for 90 per cent off the regular price. Just because they are set to expire tomorrow or the same day you purchase they sell for a few cents each. The store sells them that cheaply rather than throw them away. A long time ago people had to hunt for game or gather nuts and berries. They used a lot of energy to get their food. Nowadays we can spend practically nothing and gobble it down while watching TV.