Nice! Yes, marathon training is quite grueling and really does require proper fueling to make sure you are taking in enough nutrients to meet the demands on your body. Really any distance does if you are putting in a lot of hard work, but especially the longer distances that can put a lot of drain on your energy stores.

On the other hand, it's easy sometimes to overestimate your caloric needs, too. When I trained for my first half marathon I actually gained a few pounds because I wasn't tracking my meals and I ate with reckless abandon! Darn pancakes did me in. ;)