You know I am not a diet professional in any way, but somehow I think any young teens looking to exercise, diet and lose weight properly should talk to their Doctor about proper choices.   I worry about the increasing amount of young people who are worried about weight gain. It is not unusual for an adult woman to be in the range of 130 to 145 pounds. If you are grossly under 100 pounds, that is the weight of a child.   I only mention these things because I have two teenage daughters, one very thin, and the other a full bodied woman size. Being a full bodied woman is fine, you are beautiful!   Lastly, ask your Doctor to find you a dietician. Be healthy, be proud of who you are, enjoy your food, and try to stay active!   take care of yourself. Concerned parent.