Dude, it's simple. Talk to people, be genuinely interested in them and smile.

In High School, people usually make friends with people with the same interests as them. Thats why cheerleaders are usually friends, and why artists are usually friends too. Try to talk to people with the same interests as you.

You like working out, and I'm sure if you play a sport it shouldn't be too hard to make friends on the team.

Throughout Highschool, My friends were mostly the Art kids, until senior year, when I did the school play and made a bunch of great friends there.

You gotta get out of your comfort zone I guess. You don't wanna be stuck as the "quiet, fat kid" within right? Then don't.

What he said. ^

Or just deal with the fact that no one wants to be around you.

Only got another year or two of it anyway. Then college, where you can start over if you want.

You may not want to be that quiet kid, but unless you really make an effort not to be, then it is just who you are. It is hard to be outgoing when you just aren't. Not worth the effort in my opinion.

Join some activities you're interested to so that you'll have the opportunity to meet other people and make friends with them...