I'm not entirely sure that it's a disease, but I do agree that losing weight is a non-trivial exercise. I'm a good amount overweight myself, and it's only been due to the extremely lean times brought on bootstrapping a company that I've been able to effect meaningful weight loss.

For people that aren't overweight, here's an attempt to convey what living this way feels like:

You can't eat "normal" amounts of food. You eat, a lot, and you feel completely distracted if you can't get what you normally eat. You may eat a snack or full meal before going out with friends just so you don't look like a complete pig. Down to your last dollar, you buy a burrito and cry as you eat it, because you know that you can't afford it but it at least makes your brain stop yammering uncontrollably about needing food.

You can't wear clothing that feels good and looks attractive without doing shopping for boutique stuff. You are lucky, damned lucky, if you can find a shirt that fits and doesn't look dumb on you.

You try to go out and exercise--and you're not weak. You've probably got better-defined legs than most of your skinny friends. However, three weeks into your couch-to-5k, your knee starts freaking out and you have to stop. Pants and jeans chafe on your thigh fat if you walk long distances.

You have a constant, inexplicable negative modifier to members of the preferred gender. You can be the richest, wittiest, sweetest person they've ever met, but it feels like you must work twice as hard to be charming because they do not view you as something physically attractive, and never will. You literally are playing a shit hand in the game of life.

If you attend university, you are surrounded by happy and affluent youths who are in all likelihood much more attractive than you are and put off by your appearance (if you're a smoker, you know this feeling well). You stick out like a sore (swollen) thumb at any gathering.

You are increasingly viewed as lower class and weak-willed for your troubles. There is a very strong socioeconomic correlation with body fat percentage, and you are again a sore thumb sticking out when in the presence of happy yuppies.

You are always a silent witness to folks complaining about their own weight or making fun of your friends. The best folks will exclude you from these remarks, but that's even worse--you're simply too fat to make jokes about in good spirits, and so are excluded.

You are marketed to and pandered to in the most cynical of ways, targeted by ads that are insulting in their attempt to grab you. "Learn one funny trick to lost 5 lbs. in a week". "Eat this shake for a month to lose 20 lbs.". "Blast your abs in fourteen days." Worse, you know that you could fall for this, if things were a bit more desperate.

~

The worst part of this, of all of this, is this.

Let's say you're a hundred pounds overweight. For a male, that's about 270-280. So, if you bust your ass, you can probably get back to healthy weight (180) in nine or ten months (at ten pounds per month, which is nontrivial). Really, really bust your ass to do this.

You decide this, and the sad sorry fact is that you will not see progress of any sort for a few months. You'll be suffering for a long while, seemingly for naught, and you must bull through to make it happen. And all of the above still applies while you are trying this, and the prevailing knowledge is that you won't be able to stick to it to pull it off. And at the end of it, you'll probably be disfigured and scarred with extra skin and stretch marks.

It's fucking miserable to be a prisoner in your own body, every encounter with others a reminder of your own shortcomings and seemingly every ad or show or picture in media a confirmation that you are a failure as a human being.

Being fat sucks.