Society has long mocked fat people -- as if we don't all intrinsically understand that burritos are delicious and exercise is stupid. Truly, it's only there but for the grace of god and genetics, go we. To find out what it's actually like to live with morbid obesity, we talked to Rachel. At over 500 pounds, she's medically classified as (no joke) "super super obese," like she's some kind of bizarre superhero. We also talked to Dr. Arya Sharma and Dr. Stephanie Cassin, whose work has focused on the physical and psychological realities of severe obesity. They told us ...

5 You Don't Have to Eat That Much To Become Severely Obese You Don't Have to Eat That Much To Become Severely Obese

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The empathy-challenged of the world seem to think they've got it all figured out when it comes to staying thin: "Just put down the bucket of chicken, fatty!" But it's not that easy, and we don't mean that in a "chicken tastes good, shut up" kind of way. It starts with genetics: Scientists have found over 140 different locations along the human genome that contribute to fat location and retention, so you can be screwed in at least that many ways right off the bat.

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This little bastard has ruined more diets than pizza delivery.

That's only the beginning of your body's campaign of biological terrorism. Once that cozy layer of insulation succeeds in wrapping you up, your body will fight like hell to keep it there. According to Dr. Sharma, "It doesn't matter how you put on the weight; once you do, your physiology resets the way it works to defend the weight. And it pretty much does so permanently." He likens the process to setting a thermostat in a room. Once it's set for, say, 300 pounds, that's where your body will stay. Dieting is like opening a window -- you might catch a slight breeze, but the heater is gonna crank it up to compensate. This would be why, statistically, the success rate of every diet rounds down to zero.

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It doesn't help that lots of diets range from stupid to life-threatening.

But you have to get there in the first place, and getting there involves Hoovering up every sandwich that has the misfortune of crossing your path, right? That's why the fat guy in the movie always has an obscenely enormous, greasy cheeseburger hanging out of his disgusting maw. But Rachel is scandalized by the diets of the fictional fat, too. "I remember this one lady [on TV], she ate like a pound of bacon and a dozen eggs for breakfast, and I was like, 'Holy mother, how does she eat that much?'" she says.

"While my diet isn't great, I don't eat anywhere near that much," Rachel continues. "Maybe 3,000, 4,000 [calories] tops." That might seem like a lot, but keep in mind that you can get that many calories in one restaurant meal if you're not careful. That's how it gets you: Not in entire cases from the deli counter, but a little bit too much every day. "Many people probably assume that by the time they get to 500 pounds, they must have a diagnosable eating disorder," Dr. Cassin says, "but it turns out that many are overeating a lot at every meal, grazing." Let's do the math: One pound of fat is 3,500 calories, or 500 calories a day. That's a few cans of Coke, or two cookies from Subway. That's all it takes to gain a pound a week, or more than 50 lbs. a year. Combine that with a sedentary lifestyle of sitting in front of a computer all day (which none of us do, right?), and after a few years, you've got yourself a problem.

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There. There's what severe obesity in two years looks like.

Rachel admits that she sometimes eats too much: "If I go to Wendy's I'll get the double cheeseburger, large fries, and large Frosty," but as she points out, "that's not outside the norm of what a lot of people get." Don't try to tell us you haven't had a similar meal in the not-too-distant past. The difference is that your existing fat and your genetics aren't also punching you in the face every time you open your mouth. "People ask me 'How did you get that fat?' and it's like, it doesn't happen all at once," Rachel says. "It creeps up on you slowly, and then one day, you start having trouble walking."

But no matter how bitchin' you might turbo-charge that Rascal scooter, not being able to get around on your own is still kind of a bummer.