Marathon training and dieting.. not so easy!

So you would think running for hours on a daily basis would equal weight balance. Not really! Many people actually experience weight gain when in training. Running all those miles can make you extremely hungry. After a long run people usually spend the day relaxing and eating. Unfortunately the lighter you are the faster. So how does one actually lose weight when in training. That is the question!
I personally lost weight training for my first but I also wasn't really fueling properly until about the last month. Once I started fueling properly and getting the calories I needed my time really picked up. After my first marathon I actually gained a good amount of weight but got it off. I kept it off for NYC and have kept it off since. I still feel like I need to lose about 10 more pounds in general and it just does not want to come off. You want to get enough calories to sustain the run but not gain an ounce. A lot of people experience almost a yo-yo effect. After your long run you have lost then you creep all week until after your long run. This actually happens to me and it totally messes with my mind. It's extremely normal and happens to most. You basically store all your energy for the long run and then it all goes away. So yes you basically are a squirrel!
I personally haven't read anything that gives a definitive answer. Going based on my own knowledge, cutting calories has not worked. I'm already on an extremely healthy diet and monitored by a nutritionist. She thinks I'm fine and I need to stop worrying. Truth is I would love to lose about 30 more pounds but I've been warned that muscle weighs more than fat. She will also probably read this and I will get slammed at my next appointment. Hopefully I can get some of this weight off before Paris and maybe a little off before my half. Just some of my dumb random thoughts on training blues. Less than 3 months to my beautiful adventure and I want to be at my best!