I agree on the genetic thing. Many other factors you all know what the easy stuff is.
I'm blessed to be long and lean even though I often have cheat weeks instead of cheat meals. Cheat days are usually every other day anyway.
To demonstrate my point, My dad and uncles never worked out a day in their life intentionally other than when they are very young in the military. Yet none of them had any kind of gut on them until they were in their 60s. And that's eating good ol country home cookin.
Yet in Contrast my poor wife, who is also very lean, has to fight every day to stay that way. She's so carb sensitive that I think if a bread crumb touched her hand she's gain eight pounds of fat and six of water. She's eating a chicken breast wrapped in lettuce while I devour pisza and ice cream. It's fun.
Anyhow her mom and sisters, unlike my kin, are so fat that they have their own gravitational field. Little kids and other house items and get sucked into the gravitational pull as they merely walk by, going into orbit around the ladies forever. It giggles and wiggles too.