Weight gain from running

Question
I am a 32 year old female, and am 4' 11". My average weight has been 99lbs. Recently, i crept up to 103lbs, and i figured it was due to the holidays and the stress of my mom coming to visit. I started going to the gym 2-3 times per week. I spent 30 minutes running on the treadmill, and also did 20 minutes of stretching and Pilates.  However, my weight keeps increasing. It went to 104lbs..106.. And today 107. I am not eating extra. In fact, i have been eating healthier foods like fish, whole grains, and vegetables. I have cut out unhealthy snacking also. It has been 4 weeks since i started running at the gym. I run 5.3-6.5mph for 30 minutes. I know it is not a lot, but it is definitely more than i used to do (which was nothing). I am a college student, and spend a lot of time sitting and studying. This activity should be doing something, I'd think. At least i would think I'd be maintaining weight, not gaining weight. If i keep up this running schedule, will i stop gaining and finally start to lose pounds? Why am i gaining?

Answer
Holly, Thanks for the question. The good news is that you don't need to worry so much. It is common for this to occur when you start working out. It is partly due to the increased muscle and partly due to your body holding on to a little more water and other metabolites. It should decrease soon, but in the end the key is that you're exercising and eating better. No matter what the number on the scale says that's the most important and you're body will end up where it should be.

Good luck and don't hesitate to ask another question in the future.