There's something to the info Aunty posted, which is why I included a short anti-corporation rant in my earlier post. However, the dominant cause of overweight and obesity in the US is overeating, followed by its associate, lack of exercise.
Unless you buy exclusively organic food, which is pretty hard to do and still have an interesting diet, you're going to regularly ingest some nasty chemicals, including the kind Aunty is describing. My kids had no weight problems, primarily because their parents were also thin due to high metabolism as young people. They also were fed as healthy a diet as we could provide. My house has never had much in the way of processed food beyond canned or frozen veggies, etc. No chips, no soda; my oldest daughter wouldn't drink a sip of coke the first few times she was exposed to it. They grew up drinking water, milk, and fruit juices (no sugar added). Advertising wasn't much of an issue as we had no TV in the house, which probably eliminated 90% of the junk in American life. I never bought them video games, but we had baseball gloves, basketballs, and tennis balls and rackets, and running shoes. From this horribly deprived childhood they became adults who still aren't overweight and still play organized sports.
It's not that corporations are totally to blame. The primary responsibility is with parents. But corporations don't make the job any easier, and they do deliberately make it harder because money is more important than America to them. Pretty simple.
Sg