I went from being in the low 400's to now in the middle-low 200's (I'm a large framed 6'4, so this is a pretty decent range for me). Junk food wasn't my problem entirely, but it was part of it.
100 years from now, we'll look back on the era we're presently in as far as the behavioral neurology of obesity (and addiction science in general), how the foods around us relate to eating patterns and come to understand that we were going about treating obesity all wrong. Right now, it's a few lone voices in the wilderness being drowned out by a bunch of clueless idiots saying 'just put down the fork'...
Fact is, we still have primitive and deeply impulsive caveman brains in a thoroughly modern world. We're just now learning that people with obesity and food intake issues have entirely different brain makeups than those who don't. This is hereditary. Commercial food entities have figured out how to hijack these natural reward systems to precipitate pattern behaviors, most favorable to their bottom line. It's really no different than smoking. In exchange for their providing a substance that creates a pleasure sensation in your midbrain, you give them money.
My drug was mashed potatoes, stupid as that sounds. Back when I was at my fattest, when I would eat carbohydrates, the resulting neurochemical 'reward' was so intense I would have to go and sleep it off. Most people aren't that way.
I was able to break the cycle with willpower and LOTS of suffering but most importantly, learning how the brain works as far as this shit goes and from that point, approaching the issue with a strong understanding of what was happening with my own body when I engaged in bad pattern behaviors. Once I understood the biology of it all, it was a lot easier to confront and manage an involuntary impulse into a voluntary, deliberate behavior that I had a role in making. Strange as this sounds, once you learn what's happening in your brain, it awakens another unexpected level of consciousness in your body where you're actually physically aware of what's going on inside your head in terms of the wiring and chemicals. Hard to explain, but very interesting to experience.
Carbohydrate addiction withdrawal was immense and a bastard motherfucker. When I faltered, I turned to medicine that worked. I weaned off that, went back to willpower.
Still working.