Understanding Mildly Elevated Liver Enzymes in Teen Athletes

Question
I am 15 years old and i do swimming, cross country, and track. I recently went to the doctor and found out that I had mildly elevated liver enzymes, so she told me to eat more (because thats what she thought it was caused by)and come back the next week for a brief checkup. The next week she again tested my liver enzymes and found that they doubled. She thinks this is from a possible eating disorder, but i am at a pretty healthy wieght (5ft. 6 in. and 118 lbs) and i did eat much more the week my enzymes went up. i do not understand this. i am pretty healthy in every other way. I did some research and it said that intense exercise can increase your liver enzymes up to 6 hours after your workout and when i got my blood taked the second time, i had just swam an hour before. My doctor has taken me off of swimming untl they come back down. i really care about swimming and this is ruining my training so i want to get this problem resolved as soon as possible. i do not take any medication, drugs, or drink. do you know what might have caused this elevation? any comments would be GREATLY appreciated...and soon please--i REALLY want to swim  

Answer
dear amy:
vigorous exercise can indeed lead to mild elevation of liver enzymes. in a healthy fifteen year old i would not worry to much. infectious mononucleosis should be ruled out as this can also induce elevated liver enzymes. if you feel ok there is no reason to stop your exercising. for further information on the meaning of elevated liver enzymes look up http://www.ikp.unibe.ch/lab2/laiteste.html
best regards and wishes
swissdoc