Suspect you have a sluggish metabolism? You might have hypothyroidism, or an underactive thyroid gland, which afflicts about 25 percent of American women — many of whom don't know they have the condition, according to the American Association of Clinical Endocrinologists. "The thyroid gland controls your body's metabolism, so one of the first signs that it may be off is an inability to lose weight," explains Pamela Peeke, M.D., professor of medicine at the University of Maryland and author of Fight Fat After Forty. Your doctor can determine if you're suffering from hypothyroidism by running a blood test. If you do have an underactive thyroid, you'll be treated with a synthetic thyroid supplement, which you will need to take for the rest of your life (it will return your metabolism to normal, so it should be easier to drop unwanted pounds).
Also some research shows that the human body is primed to consume most of its calories during daylight hours. But the lifestyle is problematic for many: Because family meals and dinners with friends often are scheduled for after sunset, “people who try to stop eating after 7pm can’t do it every day for the rest of their lives,” says Dr. Seltzer, who supports an alternative strategy: Eating a hearty meal at your regular dinnertime.