I'm not sure who should we blame for obesity, but for sure in today's food there are a lot of fattening ingrediens. First of all we do have sugar now in nearly everything and we don't even notice that. There is also a lot of other unhealthy stuff, e.g animal fat which is much worse that the vegetable one. I think that we mostly put those ingredients to extend expiry date as a result we have to use preservatives. The quality of food also decreased because people want to produce it in cheapier ways so they use worse products which are more unhealthy.