metabolism is more important.
I eat what i want and i eat a lot of crap (no fast food but cookies, chocolate, cookies, ice cream and, oh yeh- cookies).
I have a high metabolism which is pushed even higher by the amount of working out i do. Some people just have lower metabolism’s which makes them more apt to weight gain.
I’m a fast burn as well. Same weight today as was in high school. I also eat what I want... I don’t expect that will change much. Older now I do find my stamina isn’t what it once was though i suspect that does drop as we age it does get annoying when a chore that once went swiftly now takes longer to complete.