Bob has a belly the size of a seedless watermelon. Bettina can't haul her groceries upstairs. Barack can't shrug without five body-language experts debating it on CNN. Bob wants to lose weight, Bettina wants to gain strength, and Barack wants to take the stress out of running for president. All three are exercising regularly … kudos! But their goals are different, and their exercise programs have to reflect that. How you exercise should depend on the results you're looking for. Your job today is to set your own fitness goals and then tweak your workout to accomplish them.

Imagine you're Bob, Bettina or Barack, and learn what you need to do get the results you want:

— To Lose Weight, Exercise Longer Or Harder. When it comes to losing weight, it all boils down to one essential truth: You've got to burn up more calories than you're taking in. Cut back your fat and food intake — smaller portions, no fried foods, bye bye, donuts, hello, peaches for dessert (rejoice that it's summer and a peach tastes … peachlike). Just as important is exercising aerobically for longer periods of time.

To get the results he wants, Bob needs to add 15-30 minutes to his workouts until he's built up to a full hour (or more) of activity five to six times a week.

If a longer workout isn't possible, then Bob needs to try interval training. That means short bursts of intense activity within the context of his usual moderate workout.

In Bob's case, he'll begin with a 5-10-minute warm-up of moderate running followed by a five-minute all-out sprint followed by five minutes or more to catch his breath followed by another sprint, and so on, for his entire 30-minute run. Bob also must be careful to not overdo it in his campaign to lose weight — push too hard, too fast — the No. 1 reason people get hurt or give up.

To Add Strength, Lift Weights. Bettina exercises three to four times a week — a mix of walking, gardening, bicycling — but she's never taken the time to work with weights. Now is the time. She's 42, and hates feeling weak and helpless. The great news is you're never too old to get stronger; people gain strength into their 90's! Bettina just needs to add one or two 15-30 minute strength training sessions to her weekly regimen. She can use free weights or machines, work out to a DVD, join a class or book a trainer.

The possibilities are endless, but the results are guaranteed: If Bettina adds targeted strength training exercises to her workout, in time, she'll fly up those stairs and feel great. She'll also significantly lower her risk of osteoporosis. And if she sticks to it, she'll wind up with rock-solid arms Madonna would kill for.

To Reduce Stress, Find A Mind Body Activity You Enjoy. Barack is stressed. OK, he has a pretty good excuse, but for the moment he represents all the millions of Americans who have our own perfectly good reasons: health woes, economic woes, housing woes. The new Toys 'R' Us is Woe is Me, and no doubt about it, all that stress is contributing to the country's high rates of illness and disease, and in Barack's case, the desire for a little nicotine.

Exercise in general is a wonderful way to deal with stress. It's a scientific fact even George W has noticed. If your doctor never mentions it and prefers to prescribe anti-depressants instead, it's time to find a more conscious doctor.

You can make your exercise routine the path to lowered stress and greater energy by adding a mind-body activity. The Eastern-oriented disciplines have introduced us sweat-loving Westerners to the mind body connection. Go for it! Yoga is great. So are Tai Chi and Chi Gong and all the other martial arts, from Aikido to zen archery. Breathing and meditation play a huge part in our physical and mental health, our energy level and sense of well-being. Pick up basketball just can't hold a candle.

Remember: If you can believe it, you can achieve it. Exercise is your dearest ally in your campaign to live a healthier life.

ENERGY EXPRESS-O! LEAVE NO CHILD A BIG BEHIND

"And so, on behalf of the President's Council on Physical Fitness, I say to America, get outside, take time out of your life, schedule yourself, do discipline and exercise." — President George W. Bush, May 5, 2007

Marilynn Preston — fitness expert, personal trainer and speaker on healthy lifestyle issues — is the creator of Energy Express, the longest-running syndicated fitness column in the country. She welcomes reader questions, which can be sent to MyEnergyExpress@aol.com. To find out more about Preston and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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