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You avoid doctors in general

You know you should eat better, exercise, lose weight, quit smoking—what more can a doctor do to help? A lot, says Dr. Nundy. Studies have shown people have a better chance of trying to quit smoking, and succeeding, when a doctor advises them to do so. Doctors can also prescribe medications that can greatly increase quitting success. And while there's unfortunately no safe pill to help people lose weight, a doctor's advice can give you a better chance of succeeding in trimming down as well, Dr. Nundy says.

Next: You don't read nutrition labels