"A large proportion of overweight individuals do not have an accurate perception of their weight status.
This underscores the need for measurement of obesity.
People in the overweight range who don't know it may not make the effort to manage their weight.
As a result, they may be at heightened risk for developing obesity and associated health problems," says Marney A. White, an obesity researcher at the Yale University School of Medicine Eating Disorders Research Program who co-authored a study in the journal Obesity Research.
More than half of all men reported they were normal weight when they were, in fact, overweight.
And almost 20 percent of men who thought they were normal weight were obese.
Body Mass Index BMI To calculate your BMI: Take your weight in pounds and multiply by 703.
Then divide this by your height in inches, and then divide that by your height in inches again.
Is Body Mass Index the perfect tool to predict whether you're at increased health risk from being overweight or obese?
For example, a bodybuilder with lots of muscle and low body fat might have the same BMI as a person who has more fat and less muscle.
Highly trained athletes typically have low body fat and more lean body mass and therefore cannot be defined by standards based on the average community.
Completed at the Johns Hopkins Bloomberg School of Public Health and published in the American Journal of Clinical Nutrition, the study looked at more than 27,000 participants.
It found that a waist of more than 40 inches for adult men or 35 inches for adult women puts them at risk for Type 2 diabetes.
Charles Stuart Platkin is a syndicated health, nutrition and fitness writer, author of the best-selling book "Breaking the Pattern," a certified personal trainer and founder of Nutricise.com.