录音1： Burning Caloreis 燃烧卡路里

Burning calories   http://vocaroo.com/player.swf?playMediaID=s1gp4AvdUscv&autoplay=0

What exactly does it mean to "burn calories" while exercising?

If I am exercising on an elliptical machine and the machine says I have burned 300 calories, does that cancel out the 300 calorie snack I had before I exercised? I feel like it doesn't but want to know what it means.
Imagine your body like a water balloon, but instead of water, it's filled with gasoline.

The gasoline is the calories you eat. Food is just energy to help your body keep running. When you eat food, you add a little water to the balloon. When you exercise, you use the water like a car uses gas in the tank. The balloon gets smaller.

Fat people have a tremendous amount of energy stored in their bodies. Skinny or athletic people have much less.

SO, burning calories means you're using more fuel then normal to exercise. When you burn off 300 calories, that means you cancelled out that snack of yours.