The higher your metabolism, the faster you will burn calories. So the obvious question is - how do you increase your metabolism? Exercise can make a big difference for several reasons.

First, it can increase the muscle component of your Lean Body Mass (LBM). Your LBM is made up of your muscles, bones, organs such as the liver and heart, and the fat stored in your heart, lungs, kidneys, intestines, muscles, nervous system and bone marrow.

The greater the muscle component of  your LBM, the higher your metabolic rate, i.e. more calories are burned. Males usually have a higher LBM (and therefore a higher metabolic rate) than females by virtue of their larger muscles. Some female athletes, however, such as swimmers and shot putters, may have a higher LBM than a male of equal weight.

You don't need to become muscle-bound to significantly raise your metabolic rate. Any exercise will tone and improve your muscle build and, as a result, burn extra calories and help use fat stores.

Second, exercise has the added advantage of increasing metabolic rate for up to 24 hours after you've finished working out, depending on how strenuous the exercise was. So when you relax in a chair after a brisk walk you are burning up more calories than the person sitting beside you who didn't exercise.

Without exercise your metabolism slows down. When you try to lose weight just by cutting calories, you actually lose muscle from your LBM as well as body fat. This has the effect of slowing down your metabolism. But if you exercise as well, then mainly body fat is lost while LBM is maintained or, more likely, increased. For this reason, exercise makes weight control easier.

The advertising claims for some diets can be quite dramatic. Claims of an 18 lb loss in two weeks are common. What is not told, is that about 13 lbs of that weight loss is fluid and muscle tissue. The overall effect is to dehydrate the body and reduce muscle tissue, the very tissue that needs to be maintained and built up. Soon the body takes steps to regain the lost water and weight begins to rise, causing frustration and disappointment.

The rapid loss in weight is seen by the body as a “famine” situation. In a concerted effort to survive, the body dramatically reduces its metabolic rate within 24-48 hours after you start dieting. The reduction in basal metabolic rate can be as high as 45%. This is exactly the opposite effect to what you want for long-term weight control.

Repeated bouts of severe calorie restriction can actually have a drastic long-term effect on weight loss. The body adapts to these constant periods of “cyclic fasting” by slowing down metabolic rate to conserve energy. The result is that diets become progressively less effective.