Trying to Lose while Training Hard

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I currently am training for a marathon and could really take a good 15lbs off before my race. The hard part is since I have been doing long miles I have put some weight on..3-5lbs. This is frustrating and can be hard on my body if the weight gain continues. I currently eat anywhere from 1600-2000 calories putting in 25miles a week of running, along with boot camps twice a week. I just feel discourage and can't find ways to control my eating with this increased exertion.