> Yeah, I put on 10 kg as well once I hit 33. I don't know what happened, everything I've read said your metabolism doesn't slow down until much later

I remained trim eating 4000ish calories a day of junk food from about age 15 to age 22 or so. Attempted to crash diet to a strict 1400 calories a day to make my comes-and-goes six-pack a bit more permanent. Kept it up for about two months. Nothing (more or less) happened. Stopped since it wasn't working. Promptly put on ten pounds. Have struggled to keep my weight under control ever since.

Metabolisms are weird.