What should you do if you're 12 years old and weigh 171 lbs and you've tried exercising and eating less but it doesn't work?

Nutrition plan is key. Its not really how much you eat it is WHAT you eat. As for the exercise, find something fun so that you forget its exercise. Play a sport, go for walks, whatever it is that you are happy to do that gets you moving around. Go see your family doctor. You may need to get your thyroid checked and the doctor may also be able to suggest a nutrition plan for you. Maintaining weight is just as mental as physical. work hard to learn how the body works and nutrition affects it. Understanding what you eat as well as how much you eat is important. Drink a lot of water-8 glasses, get an hour of good heartpumping exersize a day. I agree to develop a nutrition plan. Lots of fruits and vegetables, cut out saturated fats and sugar products will all help. Believe in yourself-you can do it!