I agree with some things mentioned here already.
When your body doesn't get enough nutrients, it starts storing calories because it doesn't know when it will get enough again. Setting up a nutritious diet is a better option. Every person's body requires different amounts of different nutrients so I recommend contacting a doctor that specializes in this or a nutritionist to find the correct combination for YOU. They will be able to help you other means of reaching your goal as well.
People that degrade you are not your friends. If you feel they ARE your friends, let them know how you feel. If they don't care, keep degrading you and etc., they still aren't your friends.
Surround yourself with positive people that will help you go in the direction you want to go and truly understand you.
Myself, I rather have no friends than fake friends/bullies.
As for strangers, you can stick up for yourself or you can accept that they don't know what they are talking about. It doesn't make it right what they say regardless.
I do a lot of what I mentioned. I surround myself with FRIENDS that don't degrade me. Sometimes I want to be alone so sometimes I'm alone. When I feel down, I avoid negative movies, music, books, people and etc. and surround myself with the opposite.
Do stuff that uplifts you instead of things that drain you, even if it means changing a lot of things and getting rid of certain people in your life.
One year, I was Hina Ichigo and then next day Temari from Naruto. While I was dressed as Temari, some girls were talking about how "that Hina" had huge boobs that were bouncing everywhere. In my opinion, not an appropriate thing for strangers to be saying. So, I tapped them on the shoulder and said "I was that Hina Ichigo". They went silent and then said "You had a very nice wig!" It felt nice to confront them and I felt a lot better.