When you’re a teenager, especially if you’re a girl, it’s deceptively easy to wreak havoc, if unintentionally, on your body. The pressure to appear flawless and to fit in without ever breaking a sweat requires putting your best poker face forward while shoving the messiness of adolescence under the bed. Skipping meals? Why not? Sticking two fingers down your throat after too many carbs? Easy as pie. Becoming a little fast and loose with alcohol and drugs, or negotiating a quick slice of the knife across your inner thigh? It happens all the time.