BMI History

Body weight and body composition have long been thought to influence health and well-being. Medical, government, public health and nutritional professionals all address the need for balance in the energy equation by keeping energy intake and expenditure in equilibrium. As the prevalence of obesity has increased, interest in methods of measuring the proportion of fat and lean body mass has also increased. Body Mass Index has limitations but provides a generally acceptable measure of body composition.

Early Measures

Body weight as a general indicator of health status is nearly universal and has been recognized for centuries. One of the first attempts to develop a height-weight table was published in 1846 by an English surgeon, John Hutchinson, who was convinced it could help detect disease and promote health.

Body Mass Index, first defined by Adolphe Quetelet in the 1860s and known at that time as Quetelet's Index, is now the primary approach to describing adiposity, according to Sareen Gropper et al. in "Advanced Nutrition and Human Metabolism."

Identification

Calculate your BMI as a ratio of your weight in kilograms divided by your height in meters squared. BMI provides an indirect measure of body fatness. Calculate and track your BMI to screen for potential weight-related health problems, according to the Centers for Disease Control and Prevention.

Interpretation

Adult weight for height guidelines have varied, but national and international groups are moving to consistent definitions of healthy weight, overweight and obesity based on BMI cutoff values. BMI for age and gender charts were developed in 2000 by the Centers for Disease Control and Prevention to enable BMI to be used to screen children for health risks. BMI is calculated the same for children as for adults, but it is interpreted differently because the normal growth pattern for children causes BMI to fluctuate throughout their growing years. BMI also varies between boys and girls. You can plot your child's BMI on CDC growth charts that describe the percentile ranking compared with other children of the same gender and age in months and years.

Changing Criteria

In 1985, an overweight BMI was defined by the National Institutes of Health as 27.8 for men and 27.3 for women, according to Robert J Kuczmarski and Katherine M Flegal in the November 2000 issue of the "American Journal of Clinical Nutrition." In 1989, the Committee on Diet and Health defined overweight BMI for all adults by age groups beginning with a BMI of 24 for ages 19 to 24 and increasing by an increment of one throughout five additional age groups, ending with a BMI of 29 for persons older than age 65.

The most commonly accepted criteria today, described in the 1987 Dietary Guidelines, define an overweight BMI as 25.0 to 29.9 and an obese BMI as 30.0 or greater. A BMI of less than 18.5 is underweight and a BMI of 18.5 to 24.9 is described as healthy.

Considerations

As the popularity of the BMI has increased, so has recognition of its limitations. Some exceptions exist for BMI interpretation with standard cutoff values. For instance, an athlete such as a bodybuilder may erroneously be classified as overweight even though he is not overfat. Conversely, BMI may be misleading for the elderly and others who have likely lost some muscle mass. In spite of these limitations, BMI has become the gold standard for assessment of weight status when used in conjunction with other diagnostic tools and health markers.