You are only 14 years old. I would like to consider it firstly. If you want to lose weight within very short period of time then you may do some heavy exercise with some cardio.
I believe you should not expect in this way. Keep in mind that it would take time if you want to lose your weight. I recommend only cardio is the best option for you according to your age. Will you like to left all of your hard working when you able to lose your extra weight? I believe not.
So think about for long term instead of short term.
In fact cardio is one of the most important things you can do for your body, whether you want to lose weight, build muscle or improve your health. The great thing is, there are plenty of choices for cardio exercise. So you have very good option.
There are some that work best if your goal is to blast calories and get in great shape:
1. Running is a great choice for a variety of reasons:
• It doesn't require special equipment (except some quality shoes)
• You can do it just about anytime, anywhere
• It's high impact, which helps build strong bones and connective tissue
• It gets your heart rate up more quickly than low or no impact exercise
• It helps you burn serious calories, especially if you add hills, sprints or try interval training.
In fact, a 145-lb person can burn 300 calories by running at 5.2 mph for 30 minutes. The same person would burn about half of that with a brisk walk.
2. If you're looking to burn maximum calories and lose your weight, cross-country skiing is an excellent choice. If possible do it. Whether you're on a gym machine or swooshing over miles of snow, cross-country skiing is an incredible cardio exercise. Because it involves both the upper and lower body, it doesn't take much work to get your heart rate up, which is where the calorie-burn comes in.
A 145-lb person burns about 330 calories during 30 minutes of skiing.
3. Whether you're outdoors or indoors, cycling is an excellent cardio workout.
By using the power of your legs, you increase endurance while burning lots of calories, anywhere from 250-500 in 30 minutes, depending on how fast you go and how high your resistance is.
4. Next to the treadmill, the elliptical trainer is the most popular cardio machine at the gym and it's no wonder. The elliptical trainer allows your body to move in a natural way, but without the impact of the treadmill. You can add intensity by increasing resistance and some machines include adjustable ramps and arm handles for added intensity as well. As a bonus, you can go backwards on an elliptical trainer, adding variety while working your muscles in a different way.
The elliptical trainer is also a good choice for runners looking for a break from pounding the pavement. A 145-lb person burns about 300 calories in 30 minutes.
5. Swimming is another great choice because, like cross-country skiing, it's a full body exercise.
The more body parts you involve in your workout, the more calories you'll burn. Spend 30 minutes doing the breastroke and you'll burn almost 400 calories.
6. Do you like kickboxing? If not you should. It would be fun I guess. Kickboxing is another great choice for exercisers who want to work hard with more choreographed workouts. Combining kicks and punches not only enhances your coordination, it involves both the upper and lower body, making this an excellent overall workout.
7. Walking is another great choice for cardio because, like running, it's accessible: You don't need special equipment and you can do it anywhere, anytime.
It's harder to get your heart rate up with walking since its low impact but, if you work hard at it, a 145-lb person can burn about 180 calories in 30 minutes.
8. Jumping rope is another calorie-scorcher and, as an added bonus, a jump rope packs easily in your suitcase, making it an excellent travel exercise.
A 145-lb person can burn a whopping 330 calories with a 30-minute workout, but you'll want to slowly work your way up to that.
Now see you have variety of option to choose. What I like to recommend you to choose any cardio you like most. Then mix it up by others in future. Initially you would not get result but you would get significant amount of result after a certain period of time.