YOUR HABIT: TRYING TO DUMP A WEEK'S WORTH OF STRESS WITH AN HOUR OF YOGA.

THE DANGER: You could end up with back or knee injuries. Osteopath Robert Gotlin, D.O., of Beth Israel Medical Center in New York City, says he sees two to three yoga-related ailments each week.

One problem is that people tend to push their bodies too far, says Dr. Gotlin. Another is that certain poses can be hard on your body if you're not very flexible: Pushing beyond your limits in the lotus pose, for instance, can strain the ligaments in your knees. To prevent this, put only one foot up on your thigh, or leave both feet on the floor, suggests Lakshmi Sutter, director of the Integral Yoga Teacher's Association near Buckingham, VA.

The cobra pose (lying on your stomach and arching your back with your hands under your shoulders) can cause back strain. Thwart stress on your lower back by keeping your weight off your hands and hugging your elbows into your body. Don't be concerned if your arms don't extend very far. And don't think that the heaters in your Bikram yoga class will automatically turn you into Gumby: "You should be able to get a little bit more stretch in a hot room, but not a lot," Dr. Gotlin says.

YOUR HABIT: CALLING JUNK FOOD "DINNER."

THE DANGER: It's no surprise that living on junk or fast food can make you overweight. But doctors are now seeing an increasing number of overweight people who are also undernourished, a problem at tributed to foods that are full of sugar, white flour, and saturated fats, making them supersize in calories but scrawny in nutrients. (Think soft drinks, pastries, hamburgers, pizza, and potato chips--the main sources of calories in the American diet.) This "high-calorie malnutrition" has several consequences, says Jacob Teitelbaum, M.D., author of From Fatigued to Fantastic! Low levels of nutrients make your brain less efficient and can leave you feeling achy, tired, depressed, and less able to handle stress.

If you occasionally must eat on the run, take a complete multivitamin daily (containing minerals and B vitamins, plus C, D, and magnesium). Remember that snack foods generally have just a fraction of the nutrients of whole foods, but if you must rely on an energy bar, choose one that offers important nutrients, including vitamin E (some contain a full-day's worth), and stay away from those that are loaded with sugar and caffeine.YOUR HABIT: LETTING "DR. WEB" DIAGNOSE YOU.

THE DANGER: Over-the-counter medicines and alternative remedies can sometimes be unnecessary, in effective, and even harmful. People who try to avoid waiting in a doctor's office by logging onto the Internet to diagnose their symptoms themselves often end up with a case of "cyberchondria"--meaning they think they have something far worse than what they've actually got, says Neil Coulson, Ph.D., of the University of Derby in England. Cyberchondria is especially likely if you start trading information with people in chat rooms or on bulletin boards. Protect yourself with common sense: It's fine to start your research on the Web, but if you're worried enough about your health problem to start popping pills, you need to talk with your doctor.

YOUR HABIT: BLOWING OFF YOUR CHECKUP.

THE DANGER: Experts predict increased rates of skin cancer, cervical cancer, and pelvic-inflammatory disease (a consequence of untreated chlamydia) in the future because of the high number of young women who don't get skin-cancer screenings, Pap tests, or pelvic exams.

Preventive care may seem time consuming and costly now (especially since people ages 19 to 29 are the fastest-growing group without health insurance), but it's far easier and cheaper to get screened than to deal with diseases not caught early. For instance, basal-cell skin-cancer surgery costs $250 to $5000; cervical cancer treatment can run about $20,000. Plus, you may be able to get a free skin-cancer screening (www.aad.org) or a low-cost Pap test (888-842-6355) if you qualify and if doctors in your area perform them.

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