Captain Cake:
I started out around 120lbs, but didn't really gain much at all for many years because I was more of a feeder type. I was actually toned, and very athletic. The thing is, spending more time around feedees and have multiple feedee girlfriends over the years, I ended up gaining some weight to around 180, and in my last relationship she basically properly pushed for me to actively gain, so the pounds rapidly piled on and I became obsessed with growing larger as all the body changes started to happen and I enjoyed them. It kind of hit me first when a friend had a bar for pull ups, and I used to be able to do many of them with ease, but when I tried it I could barely manage 1.
i had a very similar experience. i was 150ish for most of my adult life until i started seeing my most recent ex. she persuaded or influenced me to take a break from all the working out and food denial... and it has stuck, even after we split up. now i am about 340 lbs.