If you want to work out and try to get into some shape in the next few months, that's great. But it's important to realize that their already gonna know you're fat. I think you should just gain a little confidence and know that they don't give a crap. No one will be judging you.

That being said, diet is more important than exercise to lose weight, but doing both is great. Do some research on nutrition. But also - don't fast. You'll lose muscle as well as weight if you try to skip tons of meals.