how do teenagers 12-15 loose wieght? are there any special diets?!

At its most basic weight loss is all down to your daily calorie intake. If you eat less calories then your body needs you will lose weight. In this regard exercise just means you can eat more food then you could without exercise. If you’ve no interest in exercise you just need to track your calories, and aim for between 500-1000 calories below your daily maintenance level.

You can track your calories, and calculate your daily calorie requirements on one of the following sites:
http://www.livestrong.com/myplate/
http://www.sparkpeople.com/
http://www.calorieking.com.au/
I’d strongly advise you do so to begin with as it’ll give you a greater understanding of how many calories different foods have. It might surprise you how many calories foods that people consider to be healthy and ideal for weight loss actually have. For example, 100g of uncooked pasta, which is about a handful, is around 250-350 calories.

These basic steps should be enough to get you started with your weight loss, but if you want to fine tune your diet a bit there’s more you can do. The main thing you can do is reduce the amount of carbohydrates in your diet. Carbohydrates are found in foods like pasta, bread, starchy vegetables, rice, sugar, and other foods that make up a big part of the modern diet.
The problem with carbohydrates is that when you eat them your body produces insulin, and insulin plays a major role in the production and storage of fat. If you combine fat and carbohydrates in a meal then you are providing the body with everything it needs to store as much fat as possible.

Ideally you should aim for your calories to come from 40% protein, 40% fat, and 20% carbohydrates. The level of fat might seem high, but you need to remember that dietary fat is not the same as the fat in your body. When you eat fat it’s broken down and used immediately to provide energy to the body, and only stored when you are either consuming a lot of carbohydrates, or eating more calories than your body needs. If you are on a diet this won’t be a problem. You can eat whatever you like as long as you stick to this nutrition split.

The following is a list of high carbohydrate foods to avoid:
http://www.buzzle.com/articles/list-of-h…

And here’s high protein food:
http://commonsensehealth.com/Diet-and-Nu…

Next, exercise. You don’t need to exercise, but it’ll help you get fitter and improve your body shape. I’d recommend regular cardio exercise, such as jogging, or jumping rope, but high intensity stuff like Zumba will do as well, and if you enjoy it that’s even better.
I’d recommend 3 sessions of cardio exercise a week at a minimum, and if you are going to start jogging then I’d recommend the Couch to 5k plan, which is ideal for beginners :
http://www.coolrunning.com/engine/2/2_3/…

If you want a great body shape you should aim to go to the gym 3 alternate days a week, and remember the key to building muscle is doing a few sets of a low number of reps at the highest weight you can manage. People who pick up tiny weights and lift them 250 times are basically doing very inefficient cardio exercise that doesn't do anything to build muscle.

Toning is just reducing body fat and increasing muscle mass. Anything that suggests you can “tone” by doing some light weight exercise lots of time is really taking a very inefficient route to improving the shape of your body.

With weight lifting it depends whether or not you have access to a gym. If you do I suggest you follow a plan like Starting Strength, the wiki of which is full of very useful information : http://startingstrength.wikia.com/wiki/S…
The actual programme is here : http://www.startingstrength.net/workouts…

If you don't have gym access read Brain over Brawn, a free ebook, which contains lot's of useful information about dieting and weight loss : http://brainoverbrawn.com/get-the-book/
I highly recommend you read it regardless of your plans, as it will educate you on what is required to lose weight.

With a calorie controlled diet you’ll lose weight, with added cardio you’ll get fit, and with weight lifting you’ll look great, but how much you are prepared to do is up to you.

They mostly gain weight. When I was 14, I weighed only 42 kilos and I was 5'3. And I am 16 now, and weigh 51 kilos and still 5'3.

There are many advantages to losing weight and getting a healthy body. Not only will losing weight help give you the slim and lean body you've always wanted, but it will also keep away a number of obesity-related diseases you may have accquired due to being overweight. You don't need to focus on why you are fat, what you need to do is learn how to lose weight fast so that you don't get any fatter than you already are. There are many weight loss programs and plans that each cater to a different need. The best way to lose weight fast is to select the solution or system you find best suitable for you and then implement it in your daily life.
The main reason the majority of people fail at weight loss is that they don't have a proper plan defined ahead of time. Before you start applying the weight loss system you selected for youself you need to create a plan that outlines exactly what you're going to do and when you're going to do it. Failing to create a weight loss plan that you will follow is one of the easiest ways to never reach your goal and get the body you've always wanted. Basically, unless you have a clearly outline plan with specific goals and dates, then you will no doubtedly fail.
Before you learn how to lose weight fast, you need to ask yourself how bad you want to achieve your goal. Having a strong will is the only way you will be able to succesfully to go through this journey and come out on the other side. Weight loss is pretty difficult at the beginning, but once you get used to the small changes you've made in your life then you will find it easier as you go along. This is why many people decide to join weight loss support groups or camps; they need the support and encouragement from others. Even if you know exactly how to lose weight fast, you still won't burn fat if you're not motivated enough.
There are certain weight loss tips you need to follow to make sure you get the most out of your weight loss efforts. You don't need to follow the all the tips but try to make sure you try abiding by as many as possible. Though if you are serious about losing weight fast then you need to make changes in your life to follow the weight loss tips which you learn.
Being specific is very important when you want to lose weight. Not only do you need to be specific in how much weight you want to lose, but you need to also choose the method you will follow to lose weight. There are many weight loss diets for men and women, or you might be interested in other weight loss solutions. The important thing is that you see what will work best for you and then a system that fills your need.
One other thing you need to pay attention to is that you shouldn't spread yourself too thin. Choosing more than way to lose weight fast is a recipe for disaster. You can't possibly keep up with all the newest weight loss solutions that keep popping up every day, so don't try! You need to focus on only one fat loss method and then keep tweaking it untill you find yourself losing weight. Read more to find out how to lose weight fast.
There are numerous ways to lose weight fast and as mentioned above you need to choose the one that works best for you. To find a weight loss system that works best for you, ask yourself what you enjoy most. If you are food lover, then maybe going on a diet will not work for you and instead you would prefer to lose weight by exercising. Or maybe you don't have much time to exercise and aren't very picky about what you eat, in this case you could follow a healthy weight loss diet.
Most ways to lose weight fast revolve around one simple key fact, and this principle is exactly what causes you to lose weight. You will find that no matter how different two systems may be, they all aim at accomplishing this one key piece of the puzzle. But some weight loss systems abuse this key idea and offer ways to lose weight which could be very harmful to your body. You need to make sure that you follow a healthy diet or program if you want to get a lean and healthy body.
The bottom line is that unless you know how to lose weight fast and are determined to burn that extra fat off your body, then you will always be stuck with the body you have. Even if someone gave you a thousand ways to lose weight fast & weight loss tips, you still won't be able to actually lose any weight if you are not willing to put in the required effort and dedication required.

http://learnhowtoloseweight.net/ this is the site, it really works with how much weight you want to loose, it works to find you a good diet. Try it out.
Good luck :)