PE is usually taught in a manner that's great if you're already fit, and atrocious if you're fat. It's hard on the joints and exemplifies how much weaker/slower/less valuable to society you are compared to the fit kids.
I know this because I WAS fat. Horribly so. I lost nearly 100 pounds in my mid 20's by doing something simple - ignoring the exercises I hated (running, any team sports, etc.) and doing what I loved (swimming and cycling, which no PE class had offered). Instead of agonizing knee pain I experienced the joy of cycling, and instead of being a dripping sweaty pig I was in a nice cool pool, where body heat was transferred away easily.
I also quit eating the poison that some call food on a college campus. Remember that at this time people thought margarine was comparatively healthy!
(Note - I use the word "fat" because I think it's an accurate descriptor. It has unfortunately taken on a lot of emotional overtones. But let's be honest, the simplest word that describes the experience I had is "fat").