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.

CFS and weight loss

Not sure about other CFS sufferers, I myself always gain weight when my health declines. I had twice gained weight suddenly in my middle aged life: once I gained 20 lbs in 3 month and the second time was 2 years ago, I gained 10 lbs in about one months. And as soon as my health getting better, I am able to do some exercise, my weight drops.

Based on Elmer M. Cranton (http://www.drcranton.com/CFIDS.htm), yeasts mostly live around large intestine area. Thus I think that people with big waistline might carry more yeasts than those with small belly. That's why getting fat is not healthy at all. Of course there are lots of people have big belly and they are just fine, but I suspect that the reason that they are fine might be because their immue systems are strong enought to deal with that many yeasts. When yeasts grow out of proportion, which means more than their immue system can handle, they would suffer consequence just like many CFS sufferers.

Above all, everybody is different. I am glad that I don't have a very strong immue system otherwise, I may weigh 200 pounds now!