Don't worry about it. If they have moved on, well, it is their loss. You just need to take care of you right now. It would be nice to have their support, but you don't need it.
People grow apart and move on. It happens to the best of friends. If you were the "token" fat friend, as you stated, you always deserved better anyway.
You are going to do amazing, but stay the same on the inside. You will definitely meet new people that will be a healthy addition to your new lifestyle if you put yourself out there. As other posters stated, support groups are great for meeting people that are experiencing things that you have, are or will experience in the future.
Good luck, and keep up the hard work!