I think baring serious obesity , serious smoking and heavy drinking that genetics carry the most weight
Been my observances since 1957
Both my grandfathers made it to just barely past 100. They both drank and smoked plenty all their lives, but when it came to food they were the opposite of gluttons.
I remember noticing they would always take small portions or hold up their hand if they were being served. Never took second helpings - never desert - always left some on the plate, which they pushed away from them at some point.
I have no idea where those eating habits came from - they had totally different backgrounds - one came from Sweden as a young kid, the other from the Midwest. I guess they both lived through the Great Depression. Both grew up fairly poor but had success in later life.
I agree about the genetics, but it sure seems like the skinny ones live a lot longer - even if they smoke and drink.