I heard that if you want to burn calories, you should exercise at least 20 minutes. But I start to feel tired. Please tell me the truth about this.

When your body uses energy it gives off heat, and that heat is measured in units known as calories. On the other side of the equation, food provides energy. How much it provides is also measured in calories.

Here's an example that includes both sides of the calorie equation: Jogging two miles may burn off that 200 calories' worth of cookies you ate the night before.

The truth is, you're burning calories all the time, whether you're exercising or not. You just burn calories faster during (and right after) exercise. So if you can't exercise for 20 minutes, start with 5 or 10 minutes and build up slowly. Or try lowering the intensity to start.

Also, if calorie burning is what you're after, all activity burns calories. So force yourself to be more active. Park your car at the far end of the lot. Take the stairs instead of the escalator sometimes. Change TV channels without using the remote. Change your perspective on what "walking distance" is; maybe your local market is close enough to walk to.

Finally, remember what I said about burning calories even when you're not exercising? Adding a little bit of strength training to your daily regimen will make you burn more calories when you're just sitting around. Muscle is active tissue; fat is not. So if you can put on a little lean muscle mass by doing a few strength exercises, you'll enable your body to burn fuel faster. It will also help you look better.

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