Understandably for many, marathon running is more about the challenge than it is about staying fit. Often runners raise huge sums of money for their chosen charities. However for those who think it’s a healthy persuit I’d urge them to think again. Especially if interested in an attractive physique.
For the vast majority of us who won’t be making a living from running marathons we have very little reason to run this distance on a regular basis. This means that each time someone decides to run a marathon they embark on a training plan that is a stark contrast what is ‘normal’ for them. Now the body is incredibly adaptive, and in general it copes with this change. What it does mean though is you start to burn muscle that you wouldn’t otherwise. Especially towards the end of your training plan – it’s difficult to run 15+ miles and not dip into your muscle tissue. It also affects your hormone regulation. A good strategy in the gym for optimising hormone profiles is performing compound lifts with heavy weights at a high intensity for no more than 1 hour. This increases testosterone which is great for building muscle and staying lean. Long distance running doesn’t build muscle in this same way (obviously). It appears that in non-elite athletes, so that’s most people, there’s a dip in testosterone levels post-race(1). Regular marathon runners may see a decrease gonadotropin-releasing hormone(2). This can lead to infertility and, in men, hypogonadism. Lastly, perhaps least surprisingly, long distance runs increase cortisol (3). Not a huge issue, cortisol has perhaps been unnecessarily villified in the past. However prolonged cortisol levels lead to proteolysis, which can impact muscle mass.
There’s another list of reasons not to run marathons, written by Arthur De Vany. He’s a very smart guy – I’d recommend a quick glance at his Evolutionary Fitness Slideshow. He hasn’t got everything right, he makes mistakes just like everyone, but there’s a lot of good points in there.