I don’t get it either. The heaviest I got was 235 lbs, which is nearly 100 more than I weighed at my lowest. Even going from 160-180, I was wheezing while walking upstairs. 235 was the point where I became serious about exercising because I was looking at XXL clothes and 42” pants. Some people are just built differently. Smoking one American Spirit makes my fingernails slightly yellow, and I get one or two cuts in my gums, whereas I have a friend who smokes at least one pack of Marlboro Reds per day without any issues.
Back to the weight gain…it was easier for me to function in the 180s because I was still exercising and had flexibility. When I became sedentary and stopped exercising, I gained even more weight, and started having chronic back pain. That plus looking at XXL clothes, made me more motivated. I started working out my core more often and started skating again. It probably comes down to how people are built and how aware they are of their own body. I have a friend who used to be 400 lbs, 6’ 5” without any issues. We’d go on hiking/camping trips and he never had issues climbing rocks or keeping up with the crew. If you have something you enjoy, like skateboarding, it’s harder to get severely out of shape because you want to maintain the consistency of whatever activity that may be.
Edit:
I also used to drink 3 bottles of alcoholic kombucha per day and had no issues. Someone I know got bad gastrointestinal issues after just one bottle.
TLDR: People are built differently and have different tolerances. How much I used to drink on the weekends could result in death for someone else.