Hello I have had a great deal of trouble with my weight/metabolism/diet recently and I ve gone to the doctor but she hasn t helped me; I m very active and I run high school cross country, I m 5 10, and I weigh 133 lbs. At the beginning of the summer I weighed 122 and suddenly gained about 10 pounds very rapidly. All summer I had no appetite and did not eat very much, I eat between 900-1400 calories a day of healthy food and am a vegetarian. However not only has my weight not been dropping it is slowly increasing. How is this possible? I know I am undereating but I am never hungry; and my increasing weight is affecting my running very negatively. I need to find out whats wrong so I can get back to a good running weight and stop gaining random fat. Furthermore how am I gaining weight even though I am eating very little and getting exercise? That doesn t make sense. I know people who eat unhealthy foods constantly and get no exercise but are very thin; while I don t want to eat unhealthy food I do want to be able to consume enough fuel that I can run well without getting tired or being slowed down by extra weight!