So, where does this energy go (burn)?
A newborn uses most of the energy he needs to build muscles, bones, and cells for the different parts of his body. A newborn also needs the energy to spend when he cries, to breathe, for his heart to keep beating, to move his muscles, and for his organs to keep functioning. Because he does not absorb all of the calories he gets he will lose a little bit in his stools.

As you are growing you need more calories for each kilogram of your body than a person who has already grown.

What is a Kilocalorie?
When we are talking about calories we are really talking about kilocalories, or "big calories."

Basal Metabolic Rate
The Basal Metabolic Rate is the amount of energy you need to intake in your food to be able to do your routine daily required funtioning and to keep your body working (to be able to move your breathing muscles, for you heart to continue beating, for your intestine to continue to move, for all your muscles to function, and so on).

If an average woman (who needs around 2,000 calories a day) eats 3,000 calories a day she will have 1,000 excess calories. That excess has to be lost by exercising. If she don't lose it by exercising it will be stored as fat and she will become overweight.

How much energy do you spend with different activities?
For your body to stay alive (for your body functions) you need about 500 kilocalories. When you are playing you need more calories.

There are times when you need to increase your intake of calories.
For example, when you are pregnant you need more not only because you are feeding another human being, but also because your body's metabolism is on the high side so you will need more calories.

When you are extremely physically active you need a higher intake of calories to remain in balance.

How much energy do you use during exercise?
The amount of energy you use during exercise depends on the type and intensity of exercise you are doing. In general, the more aerobic the exercise, the more energy you will use.

The more intense and the longer you perform the activity, the more calories you will use.

The more you weigh, the more energy you will use when you exercise. This is good news for someone who is overweight. This person uses more energy to move his bigger weight. This is why with exercise people who are overweight will lose weight quicker than people who are close to their ideal weight.

For a comparison of activities we will use a teenage boy who weighs 125 pounds performing an activity for 1/2 hour: