> The reason marathon runners are so rail-thin is because they run a lot. Running preferentially burns muscle as well due to the quickness of conversion after glucose is gone.
I think there's some selection bias to this though. The morbidly obese tend not to be marathon runners, as well as the very muscular. Marathon running is an extreme activity that preferentially self selects certain physical attributes and conditions. This is not to say that a morbidly obese person can't take up marathon running - but they unlikely to be able to maintain it successfully while remaining so.
I think there's some selection bias to this though. The morbidly obese tend not to be marathon runners, as well as the very muscular. Marathon running is an extreme activity that preferentially self selects certain physical attributes and conditions. This is not to say that a morbidly obese person can't take up marathon running - but they unlikely to be able to maintain it successfully while remaining so.