How much weight can a 13-year-old lose in 10 days and what should they do to lose weight?

Well, In a healthy manner you just need to exercise and DO NOT STARVE yourself, it is not good for your health in the future, though fasting (not eating but drinking plenty of fluids and sometimes eating one meal) for one or two days every month or two can help you, but the fastest way and healthiest way to lose weight depends on your weight, height and age, look up calorie king and put in your info (height, age, weight) and it will tell you how many calories you can or have to eat in a day, it has helped me a lot, and I am a teenager, i have lost 30 lbs in 3 months and kept it off for the last 7 months, but just keep track of the food you eat and how healthy it is. You also need to eat at the same time everyday even if it is a snack just eat then so your body can get used to it. It may take time but being 13 it is critical to watch your weight because the fat cells you have you will have the rest of your life even if you lose weight when you get older the same fat cells will just shrink and get larger.