Moderate and regular exercise, the best way to keep you healthy!

I believe, physically speaking, 2 things dragged me into CFS: extreme lack of exercise and bad diet.
Based on yeast theory, CFS is due to the fact that increased yeast (or candida) population stresses our immune system. So, first is the increased yeasts, second is stressed immune system. I also found that lots of people carry too many yeasts but they are fine. Why? The answer is simple, because they have stronger immune system than I do. So, just one single reason, either increased yeast population or, weak immune system doesn't really cause such terrible outcome as CFS, only 2 of them get together can destroy one's health.*
For my own case, the lack of exercise caused my terribly weak immune system and the bad diet also made yeasts inside my body very happy (that's why I gained weight since I got into middle age).
Now, solutions are: diet pretty much takes care of starving yeasts; exercise would take care of improving immune system.
Here are some researches about how moderate and regular exercise can boost up immune system:
http://sportsmedicine.about.com/od/injuryprevention/a/Ex_Immunity.htm
*Of course mental issues are also very important but, I don't really want to discuss those right now.