When they make fun of you working out, keep going. When the phone rings in the middle of the workout, let it ring. This is your answer. It will take a lot of effort. But you know, it won't take nearly as much effort as everything else you've been pulling your hair out to do to try to make your life better.
Every workout makes a difference, it works.
I feel so good at the moment because I have kept up my exercising and healthy eating. I tried on some clothes last night that two weeks ago made my tummy look much bigger and guess what they look so much better. Well now I can gladly say this is no longer true. This means that I have learnt a great deal about being assertive. I hope your optimism will rub off on the rest of us.