Look, unless you have a brain tumor, thyroid disorder, incredibly specific ethnic background, or are a genetically engineered rat, you are fat because you eat too much.
This is common and really hard to resist for some people. Most, and in particular Western/American, cultures have a long tradition of food as a reward system (ice cream, pizza parties), food as celebration (Thanksgiving, birthday cake), or past-time, or comfort. There is also a strongly competitive corporate presence which continually increases portion sizes while reducing costs. This involves a lot of heavily processed ingredients, and things like HFCS and white starches have extremely high GI impacts. Things like fats, sugars, and salts are for good and obvious genetic reasons things we like and seek out.
So, you have a strong evolutionary and cultural impetus to overeat, and a ridiculously abundant food supply, where ‘healthiness’ is often inversely correlated with convenience and cost. You might get a little pudgy, a little squishy around the middle once your youthful metabolism wears off (or you might have idiot parents and start as a fat child, but that’s another matter). That’s okay. I understand.
But at what point, between getting ten and two hundred pounds overweight, do you stop and decide to really analyze your food intake? Fuck the complicated question of how you LOSE weight once you’re morbidly or even slightly obese - how did you let yourself get like that in the first place?
If you’re seriously fat, it’s because you’re lazy and you eat too much. Shot From Guns is absolutely right.
And, honestly, I’m very disappointed with your defensive internets-war capabilities, SDMB fatties.