The other day I ran 12-miles which I have not done since the late 90's. My legs felt like rubber sticks but I felt really accomplished and indeed so hungry I swear I could eat the whole fridge.
It's at these moments when you have a choice. When I trained for a marathon long time ago, I actually gained weight because I used training as an excuse to overeat, and not healthily. It's easy to justify in your head, "Oh, I just ran 10 miles, I can eat a bacon cheeseburger with garlic fries, a bowl of chili, a couple beers, and cheesecake for dessert." This is fine occasionally as 20% food, but I was eating that like every day. Even though you workout like crazy, all that work can quickly be zapped with food.