Next time you go for a checkup, don't be surprised if your doctor gets on your case about your weight. The medical profession has issued new guidelines for fighting the nation's obesity epidemic, and they urge physicians to be a lot more aggressive about helping patients drop those extra pounds. Doctors should calculate your body mass index, a weight-to-height ratio. And if you need to lose weight, they should come up with a plan and send you for counseling. "We recognize that telling patients to lose weight is not enough," said Dr. Donna Ryan, co-chair of the guidelines committee.