Noob asking probably Noob questions

I was told by a doctor to lose weigh, which has in turn made me want to take a passion (I love surf movies), and actually go do it. I've dled an app to get me started on what to expect from surf lessons I'm gonna take soon, and learn some terms so I don't feel totally noob when I'm ask if i'm goofy footed or natural and such. But after looking over the app and this site as well as others, I don't see much on preparing for surfing, as in stretching and diets if anyone is on them. Its always a good idea to stretch and exercise since surfing is a sport and sports require training to do well. But all I see is "do this type" but not some that people recommend. So any help in what stretching or exercises you all recommend or do to help me get in better shape to get the most out of surfing? Thanks in advance to any who reply. (And for the record, I am also talking to my doctor about this, but since you guys actually surf, I figure you ladies and gents have a better insight on what parts of the body is actually needed most and such.)