The Body Mass Index formula, more commonly referred to as BMI or body mass indicator, was developed by Belgium statistician Adolphe Quetelet in 1832, and was originally known as the Quetelet Index. Today, BMI is used internationally to measure appropriate weight. Your BMI can be measured using a simple equation or by using a BMI calculator. While calculating your BMI is a good way to determine if you are overweight, many factors including diet and lifestyle determine one's health. It is also important to note that what is average is not necessarily healthy.
What is Average
According to the Centers for Disease Control and Prevention, or CDC, the average American woman is 63.8 inches tall, or 5 feet and 3.8 inches tall, weighs 164.7 pounds and has a waist circumference of 37 inches. That makes the average BMI for an American woman 28.4, which is considered overweight by the CDC. Regardless of sex, the standard weight status categories are as follows: a BMI below 18.5 is underweight, a BMI of 18.5 to 24.9 is normal, a BMI of 25.0 to 29.9 is overweight and a BMI of 30.0 and above is obese.
How Your BMI is Calculated
A woman's BMI is calculated based on her height and weight. BMI is calculated differently for children and teens. Because your BMI is determined using your height to weight ratio, the average BMI for a taller woman will not be the same as the average for a shorter woman. Your BMI is determined by dividing your weight in pounds by height in inches squared and multiplying by a conversion factor of 703. For example, if you weigh 150 lbs. and are 5 feet 5 inches, or 65 inches, the equation would look like this: [150 ÷ (65)2] x 703 = 24.96, resulting in a BMI of 24.96, which is normal.
Different Body Types
Quetelet created the Quetelet Index, later renamed body mass index or BMI, because he wanted to define the characteristics of a average person. He had trouble he fitting people into a Gaussian curve due to the wide range of variables including age, stage of life and sex in to the equation. This is why it is important, especially today, to define average. According to the CDC, the number of individuals with an obese BMI increased from 56 percent in 1988 to 1994 to 64 percent in 1999 to 2000. What is "average" is changing for the worse so it is more important for your health to fall into the "normal" BMI category for your height and weight.
Average BMI By Race
According to the the National Women's Health Information Center, anyone 18 years or older with a BMI of 25 or more is at risk of early death and disability from weight-related diseases such as heart disease, diabetes, and cancer. According to the CDC, of non-Hispanic white women, 49.2 percent have a healthy BMI, 24.8 percent have an overweight BMI and 23.1 percent have an obese BMI. Among non-hispanic black women, 31.1 percent have a healthy BMI, 29.4 percent have an overweight BMI and 37.2 percent have an obese BMI. Finally, among hispanic women, 32.2 percent have a healthy BMI, 32.6 percent have an overweight BMI and 33.6 percent have an obese BMI.
Considerations
Your BMI is not an exact measure of body fatness. Generally, a person with a BMI in the obese range has excess body fat. However, individuals with a BMI in the overweight range may have excess body fat or may be more muscular. The same is true for people with a BMI in the healthy range who may have more fat than muscle. As such, your BMI, regardless of weather is is average or normal for your size, cannot be used as a diagnosis of health. Only your doctor can determine if your BMI is a healthy average for your individual age, weight and height.
References
- Oxford Journals: Adolphe Quetelet
- Centers for Disease Control and Prevention: About BMI for Adults
- Centers for Disease Control and Prevention: Body Measurements
- Centers for Disease Control and Prevention: Healthy Weight, Overweight and Obesity Among U.S. Adults
- The National Women's Health Information Center: Overweight and Obesity
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