James,
I understand your dilemma. I have a 15 year old son (white as rice), who's best friend since kindergarten is a first generation American citizen, born to parents, who fled a life in Communist China to make a new life in America, for their children.
My son's best friend is a wonderful, kind, smart, and admirable young man, and I have encouraged this friendship for him, my son and our entire family. I love him like a son, but it has been a struggle to reconcile his very rigid parents treatment of him and his younger brother.
I have actively tried over the course of 11 years to gain the trust of his mother, to prove that her son would be safe with me and my son...enjoying the simple events of elementary school through high school, that best friends do together.
I have learned that we cannot understand the deep set ideals of other cultures, and our young generation has moved into Western culture by choice. Your parents ideals of the correct body size and type is what they have been taught.
The western culture says differantly...it is OK to just be you. I think your best move is to be an active healthy young man, and share your confidence in yourself with your parents in a kind, patient, and loving way. Prove to them that you are fine, just as you are. Remember to thank them for giving you a chance to live in this new and open world. I imagine your parents made some very difficult and brave decisions, and your generation is lucky to get to change the world.
I know that my family is enriched by the deep and strong cultural influence that my son's best friend brings to us. Although I do not always understand our friends parents, I do respect their decisions, and do my best to bridge the cultural gap. Take the time to teach your parents, it will make you stronger.
You are certainly not near death, you are just beginning to live! You are just in a turning point in life...Time to grow up, and gently help your parents understand that you are perfectly happy, healthy, and excited to learn and grow. I hope that helps.