BMI and obesity Rates in the US.
Measure Your BMI.

More than 1/3 of U.S. adults are obese. But at least the rise in the country’s obesity range seems to be slowing.

34% of Americans age 20 and older were obese in 2007-2008. Add in people who are overweight and the total goes to 68%. 17% of children ages 2 through 19 were obese and 32% were overweight.

The obesity ranges were based on measuring of BMI (body mass index) of 5,555 adults and nearly 4,000 children who are considered representative of the U.S. population.

BMI correlates with the amount of body fat. Body mass index is a measure of body fat based on height and weight that applies to both adult men and women. Although BMI correlates with the amount of body fat, BMI does not directly measure body fat. As a result, some people, such as athletes, may have a BMI that identifies them as overweight even though they do not have excess body fat.

Adults with BMI of 25 to 29.9 are considered that they are overweight; body mass index of 30 and higher is defined as obesity.

Nowadays great number of Websites for weight loss programs and diet plans offer to measure your BMI for free with full diet analysis. Sources:
The Wall Street Journal
The Journal of the American Medical Association