I've been pretty much underweight my whole life, not because I had any aversion to food, was ever on a diet or anything, but I've never been a big eater and I guess I've also inherited the skinny genes. I've fantasized about gaining and getting fat (and enjoyed a couple times when I may have put on a few pounds after a period of some excessive eating on family vacation) but haven't actually cared enough to try, let alone bringing my weight up to a more average level.
Some of the benefits I've felt from being skinny are: It's feels relatively easy to run or jump spontaneously compared to heavier people. I feel like I'm getting away with something when I don't have to put in as much effort. Smaller spaces don't bother me. I don't get a sense of claustrophobia and it feels cozy. I remember being the third person having to squeeze onto a school bus seat designed for two kids because the bus was really full. Or since I do a certain amount of hands-on handiwork, getting under the sink or under a table or into an attic or crawlspace to fix something is definitely easier. Phone booths with the folding doors feel okay -- hah, not that we see those in real life anymore
Some of the downsides to being skinny: There's just a slight concern over ramming my bones into things. Like a few times I've run into a doorknob or some other object with my hip because I was going too fast and carelessly. Or like carrying a heavy wooden box and I have to support one edge with my hip while walking with it -- would probably hurt less if I had more meat on my bones. Hitting something with my elbows or the funnybone feels a bit more painful than it probably would if I had more pudge on me.
And then there's the body-confidence aspect. I'm more self-conscious about being shirtless at the pool or on the beach because I don't like the look of being able to see my ribs. I think it makes me look weak and wimpy, kind of out of line with the way I actually feel about myself.
You'd think with all these pointers I'd be motivated or interested enough to actually put on a few pounds. Guess I just have too many issues or other priorities to contend with at the moment.