For those who had fast metabolisms (always skinny) their whole lives, did you ever get fat at a certain age? Or did you stay skinny? And how old are you?

30M. I’m 6’0 and weigh 140 lbs. trying to add anything on in terms of weight is like a chore.

Will I always be lean/lanky like this? Or will I have a Santa belly when I hit retirement?😅