If you didn't realize it already, you should know that society really, really wants you to be fat. You just have to recognize that right away.
The worst thing Hollywood has ever done to fat people is portray the obese as constantly eating at every single moment. When Friends would flash back to Monica's fat days, the big joke was she always had a huge, sloppy sandwich or chicken leg in her hand. The crime here isn't that it makes fat people look like mindless gluttons, but that it sends the message that you only get fat if you eat huge comedy prop food, all day, every day.
What you find out from a program like Weight Watchers (where you are kept on a strict daily point system) is that you can get sitcom-joke fat purely by eating three meals a day of the kind of portions portrayed as normal in TV commercials and on restaurant menus.
On my first day keeping myself to the Weight Watchers system, I ate the same lunch I normally do, calculated my points, and realized I was basically done for the day. I'm not exaggerating. Under their program, the average person would get a limit of 25 or so "points" a day. A Wendy's cheeseburger is 11 points, a medium order of fries is 9. Throw in a Coke and you're done eating (and over your limit if you ate so much as a plain bagel for breakfast).