If you are an exercise dropout, a loser at weight loss, a couch potato in all seasons, the root of your problem could be much deeper than lack of time or willpower.

"Some people have a fear of success when it comes to getting fit," said clinical psychologist Ronette L. Kolotkin of the Duke University Diet and Fitness Center. Although they continually embark on weight-loss programs, a deep-seated fear of fitness dooms their diet and exercise plans.

Extra weight may serve an important function in their lives. "When you're heavy, you don't get whistled at in the street," Kolotkin noted. "People with a history of sexual abuse in childhood may begin to relive those memories when they get back in touch with their bodies through exercise and diet." To avoid that pain, they gain.

Extra pounds also may provide a ready excuse. "Heaviness can be a convenient rationale for why someone didn't get a promotion or why their boyfriend dumped them," Kolotkin said. Without that excess weight, they may have to look at other reasons they'd rather not face.

Negative childhood experiences can also play a part. "If you were a fat child . . . ridiculed and picked last for teams, you may have developed a poor body image," Kolotkin declared. As an adult, extra pounds may keep you from doing physical activity and risking further embarrassment. But not all excess weight stems from emotional conflict. "The reasons vary from deep psychological ones to making poor food choices to setting unrealistic goals," according to Kolotkin, co-author of the "Duke University Medical Center Book of Diet and Fitness."

"Many people buy into exercise myths, like there's a right way to exercise," she said.

But if you think the only "right" way is jogging, and you hate jogging, you're doomed to fail. That's why exercise programs must be individually tailored to be as enjoyable and positive as possible.

"Many overweight people have the tendency to be extremists," she observed. "They believe the old myth that if they're not suffering, they're not exercising hard enough." But that's also a set-up to drop out, since you're more likely to maintain a behavior you find enjoyable. The only "should" about exercise is to move your body for 30 to 45 minutes three to four days a week. It's important, too, to understand why you want to shape up. If you're doing it to please someone else -- your spouse, your parents or your doctor -- you may also be priming yourself for failure.

"You're more likely to succeed if you're doing it for yourself, because you want to get control of your life," said Gloria J. Edwards of the University of Michigan Obesity Rehabilitation Program. "For weight loss to be permanent, there has to be a change in your attitude about the way you eat and the meaning of food and exercise in your life."

While supportive people in your environment can aid in weight loss, Edwards believes, "relatives and close friends can also sabotage diet and exercise efforts. If you're going to the gym, they might complain, 'Why don't you spend this time with me? Aren't I as important as exercise class?' Or, 'Why are you killing yourself? I like you just as you are.' "

They may ply you with fatty foods that are family favorites, with the hidden message that if you give up these traditional foods, you're forsaking your heritage. "This is not unusual," Edwards said. "The equilibrium in any relationship changes if one person begins to change. Relatives and friends are afraid they'll lose you. So it's important to reassure {anyone} threatened by your weight loss that you'll be there for them."

If your weight-loss plans always seem to fail, experts advise:

1. Determine why you want to get fit. Is your motive strong enough to see you through the necessary lifestyle changes?

2. Find a supportive coach or teacher to help you create a personalized exercise plan. If you're embarrassed to go to a gym, consider a personal trainer. Look for an activity and place that feels safe and comfortable.

3. Seek advice from a reputable weight-loss center and/or mental health professional.

4. Take a half hour each day to do something you enjoy.

5. Don't try to lose weight by diet alone. Sensible eating and drinking combined with regular, moderate exercise is critical to losing weight and keeping it off.

Bodyworks appears on alternate Tuesdays.