1. The exercise itself uses up calories. The "average" woman uses 215 calories if she walks briskly for an hour. If this were the only physiological result from exercise-and it's not-she would burn almost 3,500 calories in sixteen days, without reducing the amount of food she eats. There are 3,500 calories in a pound of body fat, so every sixteen days, she would lose one pound of body fat. In a year, she would lose twenty-three pounds without dieting.

2. The exercise speeds up the metabolism of your muscle cells.
That's why you burn more fat awl calories when you move than when you sit still. But this elevated metabolic rate doesn't crash back to normal the moment you stop exercising. It slows down very gradually. Your muscles continue to use calories at a faster rate for as long as six hours after you stop exercising. Therefore, you burn more calories watching television or typing after exercising than you do before.

3. The exercise burns fat for fuel. In contrast, dieting triggers a starvation reflex, and your body burns muscle for fuel instead of fat. (It is saving your fat for your heart-that organ won't use anything else.) As long as you diet, you continue to lose weight, but most of that weight loss is muscle mass. Only a little fat is lost. As soon as you go off your diet, your body must replace the essential tissue it lost, and you put on 5 or 10 pounds in the first few weeks. There is no way to prevent this rebound. When you exercise, with or without dieting, your body shifts into its fat-burning phase and draws fat from every depot it can find-ugly saddlebag, thick waist, double chin, enormous buttocks. That fat stays off because the body doesn't need it. You'll put it back on only if you stop exercising or overeat.





4. The exercise builds muscle. Muscle burns calories. (Fat doesn't burn calories; it just sits there.) Therefore, the more muscle you have, the more calories you burn each day. You raise your Basal Energy Requirement, the number of calories you need each day just to stay alive. A higher BER means that you can either eat the same amount of food and lose weight or eat more food and still maintain the same weight.

5. The exercise brings your appetite into scale with your energy consumption. Most people become less hungry when they exercise regularly. The few whose appetite stays the same or increases are hungry because they need more food, not because they have the urge to overeat.
When you are sedentary, your appetite regulator, the hypothalamus, doesn't get the chemical cues it needs; it/gets stuck in the "on" position and tells you that you are hungry ~he"n you're not. When you become active, this mechanism resets itSelf. You no longer crave a doughnut two hours after you ate breakfast.

     Exercise also controls your appetite by releasing fat into your bloodstream. This fat keeps your blood-sugar level high. When your blood-sugar level is high, you feel full. When your blood-sugar level falls, you get hungry again. The new muscle fibers you grow help you use more oxygen and, therefore, burn more fat. This further maintains your blood-sugar level.