Is it true that, statistically, running a marathon actually decreases your life expectancy?

Answer 1

I don't know about "one" marathon specifically, but it's true that exercise or anything which raises your metabolism oxidizes cells and shortens life expectancy.

On the other hand, does exercise reverse disease which would normally shorten life expectancy?

The oxidation theory is the basis for VLCD (very low calorie diets). Google the terms and read for yourself.

Answer 2

That's just a silly statistic refering to people who do no exercise, like Oprah, then just suddenly jump in there and try to do a marathon.

Answer 3

Stop believing myths and hearsays and do some serious research.