I was an only child. As he got older, my father developed sort-of a big belly. But otherwise he wasn't overweight (except by today's standards.) My mother & her whole family were all slender. When I was younger I could pretty much eat anything & not gain weight. As I've aged, maintaining my weight has come to require more conscious effort.

Much as I hate to admit it, a large part of my need to keep my weight down relates to my Gender Identity Disorder. I don't look feminine under any circumstances. But I imagine that my face has, perhaps, just a tiny bit more femininity to it if I'm thin. But also, on the more practical side, I have a ruptured disc in my low back that impinges on the sciatic nerve. So keeping my weight down also helps to keep the stress on my spine as low as possible.