New BMI Standards

Stepping on the scale can be a scary event for some individuals, but it may be a predictor of health problems that lie in your future. Body mass index, or BMI, has been used in some form since the 19th century as a measurement of body fat based on height and weight. As of the year 2000, new standards lowered the BMI categorization of overweight and obese.

History

Calculating body fat based on height and weight was first invented by a 19th century Belgian named Adolphe Quetelet. Social stigmas were associated with the words "overweight" and "obese;" consequently, when obesity arrived prominently on the scene in the prospering West, this test became a tool whereby a doctor could actually assess whether an individual was too heavy or too thin. With this quantitative test, conversations could be had between doctor and patient on how to regain a healthy status.

Significance

Problems with obesity are not simply limited to America. According to Michael Pollan, author of "The Omnivores Dilemma," "The United Nations reported that in 2000 the number of people suffering from overnutrition---a billion---had officially surpassed the number suffering from malnutrition---800 million." Our ancestors struggled their whole lives to find food and now we face a time in which an array of food lines every shelf. The Centers for Disease Control and Prevention notes that overweight and obese individuals are at risk for high blood pressure, high cholesterol, gallbladder disease, type 2 diabetes, heart disease, sleep apnea and respiratory problems, stroke, osteoarthritis and some cancers. Using body mass index as an easy assessment can be a first step in health.

New standards

The NHANES Survey II remained the standard for calculating BMI until the year 2000. It held that women over a BMI of 27.3 kg/m2 and men with a BMI of 27.8 kg/m2 or greater were overweight. A benefit of these former standards was they gave men and women slightly different overweight thresholds, according to Dr. Stephen B. Halls, which allowed for the differences in genetic body composition. However, in the year 2000 the CDC and World Health Organization definition of overweight and obese changed for adults to a BMI of 25 kg/m2 and 30 kg/m2 respectively. Children under the age of 20 with a BMI greater than the 85th percentile are classified as "at risk of overweight" and above the 95th percentile as "obese." The current definition allows easy calculation and is suitable for international standardization.

Calculate your BMI

To calculate BMI you need to know your weight in kilograms and your height in meters. Next divide weight by height squared. If you are using the English system and only know your weight and height in pounds and inches, multiply by a conversion factor of 703. Therefore, take the weight in pounds and divide by the height in inches. Take the result of that calculation and divide by height again. Finally, multiply that number by 703.

Considerations

BMI is an "inexpensive and easy-to-perform method of screening for weight categories that may lead to health problems," according to the CDC. The correlation of BMI and body fat is strong; however, it can vary by age, sex and race. For example, women and elderly people tend to hold more body fat and elite athletes have a high BMI because of increased muscle as opposed to increased fat. If your BMI puts you in an at-risk category your doctor will perform further tests for a definitive diagnosis.