How can a preteen girl lose weight, say about 15 pounds?

By eating healthy.: Eliminate juices, sodas, or other sweet drinks. Drink water. Eliminate fried foods (chicken nuggets, french fries etc). Watch the sugar content in cereals and snacks. Serve fewer starches, including breads, pastas, and (white) grains. Add more vegetables and fruits, but not too many fruits because of all the sugar they contain. In short, eat an organic, whole grain, no added sugar diet.