I've always found it easy to gain weight - fat and muscle both. In high school, despite being very committed to martial arts, I was still pretty husky - caliper tested (by other high schoolers, so how accurate it was I have no idea) at around 15%. Rugby player physique - big shoulders and love handles.
I went to uni, started working out, dropped 10kgs without even knowing it and have been trying to balance things ever since. At school I didn't have much confidence at all - I was friend-zoned pretty quickly and pretty often.
Toward the end of my first year at uni I had the startling realisation that chicks were hitting on me. It took me awhile because I'd never experienced it before. I would have been looking a little more athletic than the average guy.
Since then I have periods where I put on a few extra kg's but nothing I can't reign in again with a few weeks of discipline. There was a period where I was hugely busy with work and evening study, had no time to train and had to drive around with my pants unbuttoned so i could breathe. I fucking hated myself at that point!
From what I've noticed over the years, the clearer my cheekbones, the more attention I seem to get.