Here's my theory:
The guy is a really, really mentally deranged, but smart, and dedicated "dramatic artist".
He definitely started the food abuse intentionally, but, simply by virtue of how slowly he gained weight compared to how much food he ate, he was 100% holding back outside of the camera's context.
Over time, though, he absolutely lost his grip on it, you don't post your blown out asshole on the internet without having gone too far.
He got some kind of terminal diagnostic (My guess is either circulatory or hepatic because of his eyes, I'm sure he's had AIDS forever), and was told that he'd die extremely fast if he kept going like this.
This scared him into actually stopping his "art piece", and instead, use his work ethic on extreme fat loss.
My guess? Water fasting. You can't really lose 250lbs in 7 Months under any circumstances, it's close to a pound of bodyweight a day, but if SBG is right, then it could have been done in a bit over 1 year.
If I use my estimates from my experience with water fasting, he probably needed close to 300 days.
This is
possibly also why his skin isn't hanging loose everywhere. He basically pulled an
Angus Barbieri.
The only other solution, is this was all faked on camera, but I doubt that's possible without having been caught all these years.