I am a competitive high school distance runner, racing events ranging from the 800m to the 5k. I also hope to run my first half-marathon this year. My current weekly mileage is around 35-40 miles per week. I drink plenty of water, and i eat a LOT, but very balanced with mostly healthy foods - fruits, vegetables, whole grains, lowfat/fat-free dairy, fish, nuts, eggs, lean meat - although I do have a weakness for chocolate and ice cream. Also, i'm female and 16 years old (but turning 17 soon). I am 5-foot-3-and-5/8, and weigh 110-112 pounds. Am i too heavy? would weight loss help my running performance? what would be a good weight for me?