You need to enlist the help of your parents to make sure there's healthy food provided for meals and snacks. Make sure you get enough exercise.
Ask your parents to take you to the doctor to be checked out for underlying medical issues that could cause weight gain or inability to lose weight.
Since your body isn't fully developed yet, you will need to make sure you lose weight in the proper manner, so you don't develop health issues later on.
Excerpts from the New York Times article A Call for a Low-Carb Diet 1st September 2014....
"People who avoid carbohydrates and eat more fat, even saturated fat, lose more body fat and have fewer cardiovascular risks than people who follow the low-fat diet that health authorities have favored for decades, a major new study shows."
"By the end of the yearlong trial, people in the low-carbohydrate group had lost about eight pounds more on average than those in the low-fat group. They had significantly greater reductions in body fat than the low-fat group, and improvements in lean muscle mass — even though neither group changed their levels of physical activity.
While the low-fat group did lose weight, they appeared to lose more muscle than fat. “They actually lost lean muscle mass, which is a bad thing,” Dr. Mozaffarian said. “Your balance of lean mass versus fat mass is much more important than weight. And that’s a very important finding that shows why the low-carb, high-fat group did so metabolically well.”"
"In the end, people in the low-carbohydrate group saw markers of inflammation and triglycerides — a type of fat that circulates in the blood — plunge. Their HDL, the so-called good cholesterol, rose more sharply than it did for people in the low-fat group.
Blood pressure, total cholesterol and LDL, the so-called bad cholesterol, stayed about the same for people in each group."