I read on the web the results of a medical study. It said that men who were fit (exercised a certain amount) had half the chance of dying in the next 10 years as unfit men. It also said that men who were very fit had 70% less of a chance of dying in the next 10 years. I assume that these were men of at least middle years and not 10 year olds. At any rate, the conclusion was that exercise has a direct benefit on health. Sometimes I think physicians should not be allowed to make conclusions.

The problem with the above studies is the results do not demonstrate any survival advantage as a result of exercise. How can I say that?

Well because

Very fit men probably have much lower rates of diabetes than the normal population and diabetes raises mortality rates.
Very fit men probably are not excessively obese and obesity is associated with higher mortality.
I would just bet that very fit men have hearts that are in better shape and less chance of a fatal heart attack.
I would just bet that very fit men probably are not suffering from advanced cancer.
I would just bet that very fit men probably have very low rates of smoking.
I would just bet that very fit men probably have lower rates of alcoholism.
I would just bet that very fit men pay more attention to having a healthy diet.

Unless you control for all of the above, and the study did not indicate that it did, then the improved advantage to fitness could well be just other beneficial things that are associated with being fit and not a result of the exercise in and of itself.

Now I am very fit and I would like to think that is a good thing. But I am very skeptical of the sloppy research that is often done.