Let's face it, first impressions are lasting impressions. If you walk into a meeting or a job interview looking burned out and off your game, you've got two strikes against you before you say "Hello."

How then do you dazzle them with healthy good looks? How do you make your skin look moist and young, and get that pink-cheeked pep? How do you keep your hair and nails in great shape, and increase your agility and grace?

How do you put sparkle in your eyes and bounce in your step?

How do you exude a sense of energy and well-being?

There's only one method I know for all the above: regular daily exercise. This is a fact, Jack! This is a fact, Jill!

Hot off the presses: A 2009 study at the University of California at Los Angeles based on an analysis of 94 brain scans indicates that obese people have 8 percent less brain tissue than people of normal weight. And more: The brains of obese persons are biologically 18 years older than the brains of thin persons.

"That's a big loss of tissue," says Paul Thompson, professor of neurology at UCLA and author of the study. "It depletes your cognitive reserves, putting you at much greater risk of Alzheimer's and other diseases that attack the brain."

Being overweight increases your chances of heart attack, high blood pressure, diabetes, and several types of cancers. People, there are only two ways I know to keep your tummy tamed: proper diet and regular exercise.

Thousands of scientific studies have proven that even 10 or 15 minutes of intense exercise a day stimulates your brain to release a bath of powerful neurotransmitters like dopamine, serotonin, and norepinephrine.

These brain chemicals fight depression, relax muscles, and stabilize mood. Along with endorphins, the body's natural painkillers, they produce that special feeling of calm and well-being you get after a workout—that exerciser's euphoria and runner's high. I can say with all honesty that I always feel happier and more relaxed after I spend an hour in the gym. You probably feel the same.

And isn't this what selling is all about? A relaxed, can-do, optimistic attitude? "The very definition of a salesman," says Zig Ziglar, "is a person who is both happy to see you, and happy in his own skin. You sense it in him, and it favors you in his direction."

Where does our energy come from? Some people think we get it from stimulants like coffee, sugar, or pills. But this is a fallacy. Stimulants simply slurp up the energy that's already inside us, which is why when you come down from stimulants you feel so tired and depleted.

True physical energy is derived from the food you eat and from regular physical activity.

Studies show that exercise speeds up metabolism, increases blood flow, and brings energizing stores of oxygen to the brain. It also fires up tiny centers known as mitochondria inside each cell in our bodies. These cells within cells act like miniature power plants, generating energy that sparks the nervous system and helps overcome stress and fatigue. The more you exercise, the more mitochondria your body produces. It's a seriously amazing self-generating cycle. Energy makes energy, which makes more energy. The more you work out, the better you think, feel, and do.

When you're stuck in traffic driving to the office, when work piles up on your desk, when coworkers are in our face, your body tenses up and bad things happen. It starts with the adrenal glands. When the pressure's on, they pump too much adrenaline into your bloodstream. This increases heart rate, raises blood pressure, and gives you those chalk-on-a-blackboard feelings of anxiety. The stress hormone cortisol is also released when stress comes, making you jumpy, irritable, and, over the long haul, downright sick. That's no good.

Exercise to the rescue. Regular workouts reduce cortisol levels, rid the blood of tension-causing lactic acid, lower blood pressure, and act as an overall counter to the nasty things that stress does to you. One more good reason to stay in shape.

A 2005 study found that each year obesity and lack of physical activity cost American employers $11 billion in lost work hours. Each year $10 billion is spent on medical care for sick employees alone.

Many American companies have been proactive in promoting wellness in their offices or factories. Weight loss and stop-smoking plans, on-site exercise facilities, yoga classes, walking programs, healthy food choices in the cafeteria, and innovative on-site fitness devices like treadmill desks all lead to a healthier workforce.

Yet as economic times darken, higher costs have made this perk into an endangered species. And that's a shame. Businesses need these programs to keep employees happy and on the job. It would be a terrific idea if American companies avoided the penny wise and pound foolish route, and realized that spending a few dollars on company health generates big financial long-term rewards in the form of fewer workdays lost and more productive employees who simply do their jobs better.

Exercise calms your busy mind, and makes your body ready for sleep. It lessens anxiety and depression, two major causes of insomnia. Daily physical exertion increases the amount of time you spend in the deepest sleep states. That's a big benefit. We like that. If you're well rested, you won't nod off at your desk or head to Starbucks for sugar and caffeine. If you're well slept, you're less likely to be hungry, a plus for keeping slim. Deep sleep boosts your immune system and heightens your stamina. Sick days become a thing of the past, and you don't live in terror of the latest flu of the month. Work out to sleep well. The two go together.

One of the most exciting discoveries made by science in the past decade is that regular exercise actually creates new brain cells. Known scientifically as neurogenesis, this process occurs mainly in the learning and memory centers of the brain. The more you exercise, the stronger both functions become. Working out brings fresh blood to the brain, increases circulation, and gets rid of the toxic wastes that build up from the day's mental activity. You learn better and you remember better. "Physical fitness," President John F. Kennedy once remarked, "is not only one of the most important keys to a healthy body; it is the basis of dynamic and creative intellectual activity."

Fitness, in short, makes you smarter. It helps you think better, helps you recall facts more rapidly, and helps you concentrate for longer periods of time. What incredible benefits! Take advantage of them.

There's something about a person who's in great shape and knows it. A kind of power radiates from these people. Others sense it and are attracted to it.

When you look your best; when your body image wins approving glances; when you're blasting out energy and enthusiasm; when everything feels strong, light, agile, and tawny inside—you automatically feel a whole lot better about yourself. How can you afford not to take advantage of this remarkable gift from nature? How can you afford—and I mean this in dollars and cents as well as improved health—not to keep fit?