OK first and foremost, because you're so young and you're asking this question, it concerns me. Please just realize that the only way you will stay in shape consistently is if you do it for more than just looking good. You have to have more motivation. You have to stay in shape because a healthy body promotes a healthy mind and soul. Staying in shape helps you with ALL aspects of life. It gives you more energy and more motivation to complete goals, relieves tons of stress and allows your mind to be clear .
On that note, eat right. I remember at your age I ate like crap all the time. Make an effort to eat as many raw veggies and fruits you can. Stay away from too much bread and dairy. They can be extremely fattening if overeaten. When you're full, STOP EATING!! And as for exercising, you have to make it a part of your daily schedule. Walk to school, play outside (I'm 24 and I play outside), dance, garden... Whatever! In my experience exercising at a gym is nothing but work work work and I can never fully enjoy it. You have to move your body in a way that YOU enjoy. Running in place next to 15 other people running in place is not fun. So get out and live an active lifestyle. No diets!!!
On that note, eat right. I remember at your age I ate like crap all the time. Make an effort to eat as many raw veggies and fruits you can. Stay away from too much bread and dairy. They can be extremely fattening if overeaten. When you're full, STOP EATING!! And as for exercising, you have to make it a part of your daily schedule. Walk to school, play outside (I'm 24 and I play outside), dance, garden... Whatever! In my experience exercising at a gym is nothing but work work work and I can never fully enjoy it. You have to move your body in a way that YOU enjoy. Running in place next to 15 other people running in place is not fun. So get out and live an active lifestyle. No diets!!!