Have to disagree. Not genetic. Obesity wasn't some "sleeper" gene that simply lay dormant until fast food became readily available to us.
We're fat because many people don't want to take/make the time to cook themselves some healthy food. Simple as that. Fat people breed fat kids usually because they never learned how to eat right or cook healthy foods themselves. Hate to get political, but I don't want it to become a legal disability and have more lazy people see it as an option to not work. Alright I'll get off my soapbox.