You know it's important to exercise, but do you know why? If only a few reasons come to mind, read on. Reviewing the enormous health-promoting benefits of exercise may encourage you - as an investment in your SELF - to include exercise in your daily routine.

- Exercise boosts brain power, bringing an increase of blood and oxygen to the brain, thus giving a person an "intellectual edge."- Exercise allows you to use nutrients to their maximum efficiency. Putting nutrients into your body without physical activity is like putting gasoline in a car and leaving it in the driveway.

- Exercise is an energy investment with high returns.

Says Kenneth Cooper, M.D.: "Like a well-tuned engine that uses less oil and gasoline, a well-tuned body uses less energy to perform daily functions . . .. Toned muscles make every movement - from lifting a pencil to walking up a flight of stairs - relatively effortless."

Cooper, author of "The Aerobic Program for Total Well Being," also emphasizes: "A conditioned heart - which pumps more blood with each stroke - doesn't have to work as hard, circulating the same volume of blood with fewer strokes."

And a fit heart, with its lower heart rate, provides a form of stress resistance. "A lower heart rate during stress means you tend to stay calmer and more in control of your emotions. But there are even more important consequences. To put it bluntly, a well-conditioned heart may save a person's life."

- Exercise is a potent antidote for depression. One way of erasing - and even preventing - periodic lows is to GET MOVING. Research conducted by Robert Brown, Ph.D., M.D., professor at the University of Virginia, showed that aerobic exercising markedly decreases depression. Of 2,000 students and patients studied, 40 to 50 percent showed significant improvement in mood after three months of such exercise.

- Exercising creates a sense of empowerment, reports Brown, "giving you a feeling of accomplishment and mastery that puts you back in the driver's seat of life and gives you a feeling of control, decreasing that feeling of hopelessness and helplessness depressed people have."

- Exercising also imbues people with what one medical expert calls a capacity to change. Speaking of runners, this expert says that they "learn, often dramatically, that they can change themselves for the better."

Running improves physical health, appearance and body image, and also increases self-acceptance.

- Exercise produces a lasting euphoric effect, reducing chances you'll eat to relieve anxiety, anger, frustration or depression. Studies, in fact, show that vigorous workouts can increase stress- and depression-fighting endorphin levels in the bloodstream as much as fivefold.

- Exercise depresses your appetite by stabilizing insulin (your hunger hormone) and your blood sugar and makes you feel fuller when you eat by stimulating the production of hormones that raise the blood-fat level.

- Exercise allows your body to burn extra calories for up to 15 hours after you stop exercising. Exercising in the morning and at night gives you calorie-burning benefits 24 hours a day. Exercise can also boost your metabolism 20 to 30 percent.

- Exercise burns FAT. Ounce for ounce, fat contains more than twice the calories than other foods; one gram of fat contains nine calories, while one gram of protein or carbohydrate contains only four. So to get rid of fat you have to burn twice as many calories. Dieting - without exercise - is inefficient in burning fat calories. When you diet, your body first uses up glycogen (a form of stored sugar), protein and water. Only after several weeks on a diet does your body release body fat for its energy needs.

But - if you add exercise - your body burns fat while it builds or at least preserves muscle. Studies show that when dieters add exercise, they lose significantly more fat and less muscle tissue.

If you add up all the benefits, you can see that exercise is vital to your well-being. Unfortunately, when people go into overload, they usually eliminate exercise - the very energy booster they need.

So are you ready to exercise your cares away? If you're a non-exerciser, do I hear an "Ugh?" But just think - how can you resist the immense benefits of exercise that have been so painstakingly laid out before you? Just try a few easy bends and stretches, maybe a jog around the house or block. Start easy and work up. Remember: ANY exercise helps.

If feasible, move eventually to any good aerobic exercise that speeds up your heart and breathing rate.

Alternate several kinds of exercise you'll enjoy - jogging, walking, swimming, dancing, cycling. Do aerobic exercise at a minimum of 20 minutes a day, 4 days a week. An optimum would be 30 minutes a day, six times a week.

But, build slowly, and don't overdo. Strenuous exercise can cause "sports anemia." The symptoms: weakness, fatigue and irritability.