I believe it can easily be an self-imposed addiction. I believe a minority really can't help it, usually those with medical problems that makes it extremely difficult. However, I believe for a majority eating right, exercising, and just generally leading a healthy life-style will help them in losing weight, whether it's 100lbs or just 20lbs, they earned it and should be proud of themselves; regardless of what anyone else says. You can still be hefty, stocky, and a thicker person while living that healthy lifestyle. However, I believe a majority of people tend to put way too much emphasis into; "It's my genes!", "It's my bones!", "It's my body structure!" and they end up not even trying.
I myself was addicted to food and I'd use it to self-medicate myself (ALONG with drinking and smoking). Like some people do with cigarettes, drugs, and alcohol. I was 100lbs overweight by being 245lbs, at the height of 5'5". I banged all of the same drums. Genetics, bones, body-structure. I am now 168lbs and closing in on the personal goal I set for myself (145lbs), which means I've managed to lose 77lbs. I quit smoking and drinking. No gym, no crazy workout fads or diet crazes. I worked out at home, studied plant-based nutrition, and used that as a guide to eat as healthy as I possibly could. I still do. "You can have just one, you've been so good!" is a constantly repeated phrase that ends up haunting me. I find that I can't indulge like other people even with a simple snack-sized bag of chips even having just one beer or two beers with friends is something that requires a dedicated workout later, however I can also be personally blamed for running my metabolism right into the ground, even if it wasn't that fast to begin with.
I caught a lot of hate from my family, who also always blamed genetics for their physical appearance; because I asked them to please lead healthier lifestyles. My family (besides my dad who has always been healthy) are yo-yo dieters. If something doesn't work to their expectations that week, they'll move on to some other crazy diet phase. Eventually they gain whatever they did manage to lose back and say, "See, it's my genes! Exercise and eating right doesn't work!" Except it actually can, if you can muster the self-control. As my cousin and sister proved to themselves.
As long as you eat right, exercise, and generally live a healthy life-style your body will reflect that, size 0 to 12.