I did go through a similar phase during my teen years, since I was fat as well and not because I ate too much but due to a hormonal imbalance that never got rectified. Society is nothing but people with hollow hearts that constantly look for things to fill their void even at someone else's expense. I stopped looking at the mirror and made a pact to myself that I am who I am and don't give a dash to what others may think of me. It doesn't change their perspective, but it sure helps me.
An incident that recently happened, one of my friends who suffered from obesity her entire life have recently started to lose weight. I never ever in our friendship ever said or hinted at her weight. In fact I always encouraged her persona and gave her compliments on her other qualities. I recently met her after a year and recently i had put on some weight due to my kidney stone issue. I complimented her that she looked good and in return the first thing out of her mouth is, but you have put on weight. I was a bit shaken, but I smiled and moved on.
So no matter what you do ppl will have the obnoxious audacity to pull you down as they cannot stand the fact that you might turn towards getting better than them.
You are a beautiful soul and kindness is far, far superior to any outer beauty. And that what really matters.