Body Mass Index (BMI) is a measurement based on an individual's weight and height. Typically BMI is used to assess an individual's risk for health complications that are associated with persons of higher body weight. For adults, the BMI calculation is not dependant on age or sex. There are more precise ways to measure body fat such as skin fold measurements using calipers and other more involved scientific methods, but for most uses, BMI is the fastest and most inexpensive and can still yield fairly accurate results.
The formula for body mass index dates back to the 19th century when Adolphe Quetelet first derived it for use in the developing field of "social physics". Initially his formula was intended to classify sedentary (physically inactive) people into three classes: underweight, healthy weight and overweight.
The term "body mass index" was first coined in 1972 by Ancel Keys who felt that BMI was appropriate for population studies, but inappropriate for individual diagnosis. However, due to its ease of use and calculation, body mass index has been propagated by physicians and fitness professionals in diagnosis of individual's weight and fitness goals.
While body mass index remains suitable for making generalizations about an average person's weight there are some cases where body mass can result in classifying a healthy adult as overweight or even obese. Individuals with an athletic physique (more than average musculature) tend to be categorized as overweight since their additional muscle skews the weight/height ratio. In addition to athletic physiques, individuals who are either abnormally short or tall can also have BMI results that would yield an unrealistic weight range. Senior citizens tend to posses more body fat than younger adults giving them a higher than normal BMI results.
BMI remains an adequate weight classification for most people but as with any weightloss or fitness plan, you should consult your physician prior to beginning any new weightloss or fitness routines.
Interested in finding out how your BMI translates into an ideal weight? Use our ideal weight calculator to find your "ideal weight" range.