Don't wait to weigh: Check the chart, then step on the scale. Thoughts to yourself: "Most of my clothes still fit, and the nurse didn't gasp the last time she had me on the scale. I couldn't be overweight!"

Maybe.

The National Heart, Lung, and Blood Institute issued the first-ever federal guidelines defining overweight and obesity this summer. More than half of U.S. adults -- 97 million people -- are overweight. Dr. Scott Grundy, director of the Center for Human Nutrition, was a member of the expert panel that issued the report, designed to help physicians care for overweight and obese patients.

"Obesity is more than a cosmetic problem," said Dr. Grundy. "It contributes to heart disease, diabetes and other chronic conditions."The guidelines are based on the most extensive review of the scientific evidence on overweight and obesity conducted to date. Overweight is defined as having a body mass index (BMI) of 25 to 29.9 kilograms/meters2; while obesity is a BMI greater than 30 kilograms/meters2. Some muscular people may have a high BMI without health risks. People of normal weight should have their BMI reassessed every two years.

Additionally the panel noted that a waist circumference of 40 inches or more for men and 354 inches or more for women is associated with increased disease risk in those who have a BMI of 25 to 34.9.

To determine BMI, divide your weight in kilograms by your height in meters squared.