Okay but I think… Ford was pretty fit pre-mental breakdown.
I don’t think he had much of a gut, and was pretty slim. Obviously, he put on a bit of weight during college, but who doesn’t?
(I also think his body in the college pic from TBoB may have just been an oversight since it had been years since they’d written the show/Journal 3 and added those details, and he was still relatively slim here at the end of college in the show)
But when he was in Gravity Falls, he was constantly hiking around, chasing various anomalies
He even states in Journal 3 that he had a rigorous daily physical (and mental) workout, despite having hated physical activity when he was younger.
It sounds like he ends up approaching exercise with the same rigor he does his studies, namely because it is a means to further his research. He can’t do half of what he does if he isn’t in peak physical shape to keep up with the anomalies and go on field research trips. Based on his words there, I think it’s safe to assume.
And he says that a few months before the falling out with Bill.
So when his life falls apart, he stops exercising and starts eating junk (as one does).
And he puts on some weight, which leads to his body in this picture
He also had no control over whatever Bill was shoveling into his mouth when he possessed him, and Bill would ignore body cues that told him he was overeating. He was just tossing shit down Ford’s throat with no care for how it would affect him when he woke up (and actually hoping it would be something that hurt him)
So he probably contributed a LOT, in ways other than just by totally betraying Ford, taking advantage of him, and causing a catastrophic meltdown
