Doctors use body mass index to measure your weight relative to your height. Calculated as a ratio of weight to height, your BMI is an indication of whether you are maintaining a healthy weight. While this measure has long been considered an accurate measure of health risk in all adults, a healthy BMI differs with age and sex, and may underestimate obesity in women.
Calculating BMI
You can calculate your own BMI using either the metric or conventional American system of measure. To determine the ratio using metric measure, divide your weight in kilograms by your height in meters, squared. In the conventional American system, take your weight in pounds and divide it by your height in inches, squared, then multiply it by 703. Online calculators at the CDC and American Dietetic Association websites can assist you in measuring your BMI.
Classification and Disease Risk
BMI is not a measure of body fat or physical fitness, but a ratio of weight to height. For example. a bodybuilder with a BMI of 25 or more but low body fat is still considered overweight. People with a BMI of 18.4 or lower are considered underweight; from 18.5 to 24.9 are at normal weight; 25 to 29.9 are overweight; and at 30 or more are labeled as obese.
As BMI increases, so does a women's risk of dangerous health conditions. According to WomensHealth.gov, which is operated by the U.S. Department of Health and Human Services, women with high BMIs are at a higher risk of developing heart disease, stroke, Type 2 diabetes, hypertension, arthritis, gallbladder disease and some forms of cancer.
Considerations
While BMI is a ratio, body fat percentages determine how much of the body's weight is made up of fat, as opposed to muscle or water. According to HealthCentral, body fat rates can be determined with body scans, ultrasounds, specialized scales or taking circumference measurements of the neck, waist and hips. Healthy body fat percentages in women range from 19 percent for women of African descent to 22 percent for Caucasians to 25 percent for women of Asian heritage.
Writing for MayoClinic.com, nutritionists Jennifer Nelson and Katherine Zeratsky reported on a 2010 study showing that BMI is not an accurate measure of obesity in women 20 to 33. Based on BMI alone, 37 percent of study participants scored in the obese range. When body scans were used to measure fat composition, that number increased to 63 percent.
Influences
Healthy BMI measurements in women correlate to the availability of fresh fruits and vegetables and healthy food. A study published in the June 2010 edition of "Journal of Planning Education and Research" linked food environment with female BMIs. Researchers at the University of Buffalo in New York found that women who lived closer to a supermarket, as opposed to a convenience store, had lower BMIs. They concluded that a positive food geography promoted healthy lifestyle choices.
References
- Centers for Disease Control and Prevention: About BMI for Adults
- MayoClinic.com: BMI May Underestimate Obesity in Women
- WomensHealth.gov: Overweight, Obesity, and Weight Loss
- "Journal of Planning Education and Research"; Food Environment, Built Environment, and Women's BMI...; S. Raja, et al; Jun. 2010
- HealthCentral: Home Body Fat Test
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