How can I get thin fast please help??????

By thin i don't mean supermodel skinny, i mean healthy and toned. Currently I'm about 5ft tall, and I weigh 110 pounds and I'm 14 years old. A lot of my friends are thin and tall and beautiful, while I'm short and stubby. I'm not fat, I'm size extra small in most stores and a size 3 to 4 in jeans. I don't wanna loose too much weight just enough to have a flat stomach and no arm flab. thanks :)