I don't think just puberty would have caused my weight gain. If I had been eating normally at the time instead of microwave dinners every night while my mom was sleeping off her depression, I probably would have been OK.
OTOH, my chemical imbalance certainly made things much worse. I posted that after I got on anti-depressants, I gained 75 pounds in less than a year. My out look improved vastly when I corrected my brain chemical levels, but the eating just worsened. I am convinced that since the emotional levels, sleep levels, and appetite areas are all affected by SSRIs any change in one is going to lead to a change in the others for me whether for good or bad