nutrition and endurance training

Question
I am a 25-year-old female and have always naturally been very thin.  I run about 12 miles a week, and ran a 10K last year.  I would like to increase my mileage and start training for a half-marathon.  My problem is, I have a small appetite and only eat about 1500-2000 calories a day (I've never really counted.)  I have a hard time eating any more than that.  I get too full or I just don't feel well.  If I exercise regularly or especially when I increase my level of exercise, I start losing weight, even though I don't have weight to lose and my bmi is already bordering on too low.  My question is, how can I increase my level of exercise without losing weight, or is this possible in my case?  Or is there a simple way to increase my calorie intake without eating more (i.e., a specific high-calorie food item or power bar or something) so that I can keep up with my increased metabolism?  This is becoming a serious problem for me!  (Probably about a million people out there would kill for my "problem", huh?) :)

Answer
Dear jenny
   I do not see a problem at all.
First of all when you increase your mileage you body is going to adapt to it and you will want to eat  more and you will need to eat more to matain your increase in mileage.If your losing weight your not eating enough.If your eating the right combination of quality food in carbs.protein.good fats you will have no problem.It is a balancing act as you increase your mileage and will take a little time to ajust....Just do not stress about it.Your body and mind will adapt to your new level of fitness/
My one recomendation to insure saftey is go get your body fat taken from a sourse who uses calipers.A friend of mind who holds the world record in the womens marathon and won new york city nov, 7th matains a body fat at about nine percent.You can check out her web site at wwwpaularadcliffe.com..She trains here in albuquerque new mexico where i live all the time.

I hope this gives you some insight jenny.Let me know how your doing and if there is any thing else you no where to come.

The very best to you
John
www.rentacoachinternational.com