In theory, people should be able to glance in a mirror and see they're packing extra pounds. But 30 percent of overweight Americans think they're at a normal weight, according to a recent poll from Harris Interactive/HealthDay. Here's how to take a more honest look:

• Don't compare yourself to others. So many Americans are overweight now that you may get a skewed sense of what's healthy. "The normal reaction is to say, 'My child may be a little chunky, but they aren't as big as that kid over there,"' said Babs Benson, a registered nurse and manager of the "Healthy You" weight management program at Children's Hospital of the King's Daughters in Norfolk, Va.

• Figure out your BMI. That's body mass index, a measurement that considers both height and weight. To find easy-to-use programs and result analyses, type "BMI Calculator" into an online search engine.

• Measure your waistline. Abdominal fat is most dangerous because it raises the risk of heart disease and diabetes. Wrap a tape measure around the smallest area between your rib cage and belly button. Men should measure no more than 40 inches, while women should be 35 inches or less.

• Consider your waist-to-hip ratio. It's better to have big hips and a smaller waist than vice versa. Divide your waist measurement by your hip measurement. Ideally, woman's result should be 0.8 inches or less and a man's 0.95 inches or less.

• Work with a doctor. Medical professionals can take accurate body fat measurements and plot BMI readings on a detailed graph. "It puts the whole thing into perspective," Benson said.

• Look at pictures of yourself. Many people first realize they're too heavy when they see themselves in recent photographs.