You need to tell me why people gain weight while training for a marathon...I am ok with it, if I know it peels off as soon as you are finished training.
That's a good question, especially when you see elite marathoners who look more like twigs than women (these women are on strict diets and limit their caloric intake to bare minimum). I usually gain weight when running longer distances because I need more calories to go the distance. If my caloric intake is the same as my 5k training weight I get really worn out on the long runs and usually get deep, painful side aches that last for days. You'd also assume that because you're running more, you'd burn off the extra calories you're consuming...not so my friend. I have yet to discover the theory behind this idea, perhaps I'll call it the Caloric Freeze Theory for now, but even though you are technically burning off more calories, it doesn't seem to compensate for the additional dietary intake.
The weight has always come back off for me once I resume my normal caloric intake and 5-10k training schedule. This seems to be the case with many others I have conversed with as well.