Bmi Calculations For Women

Body mass index, or BMI, is a ratio based on your weight and height. Doctors use BMI values to quickly estimate the amount of fat in the body, as this method closely approximates more direct, costly and time-consuming measures. Although doctors use the same BMI formula and categories for all adults, women naturally tend to have more body fat than men. As such, you may need to use adjusted BMI ranges to accurately assess your risk of health conditions related to obesity and or being overweight.

Calculation and Categories

To calculate your BMI, begin by multiplying your weight in pounds by 703. Divide this number by the square of your height in inches to arrive at your BMI value. For both men and women, the Centers for Disease Control and Prevention, or CDC, consider you to be underweight if this value is below 18.5. If your BMI is between 18.5 and 24.9, you are at the normal or ideal weight for your height. Values between 25 and 29.9 indicate that you are overweight, while you may be obese if your BMI is greater than 30.

Overweight and Obese

Approximately two-thirds of Americans are overweight, with nearly one-third of them having BMI values over 30. While more men are overweight, women account for a greater percentage of obese people in the U.S. However, as women tend to carry more body fat than men at the same BMI, these values limit the tool's accuracy as a measure of body fatness. For example, while a woman and man may both have normal BMI values of 24.7, the woman's higher body fat percentage may place her at higher risk of developing health problems such as heart disease, high blood pressure and type II diabetes.

Underweight

While the risks of being overweight are considerable, the risks of a woman being underweight are much more serious. Although you may be healthy at a lower BMI if you are naturally slight of frame, an early sign that you are at a dangerously low weight is menstrual irregularities. This may lead your periods to stop altogether, possibly leading to infertility or problems becoming pregnant later in life. If your low weight is due to malnutrition, you may increase your risk of becoming anemic and developing osteoporosis early in life, both of which are more likely to affect women than men.

Adult Women

According to a research review by Dr. Steven Halls, the CDC's BMI ranges are particularly accurate for men and women at age 18, with this accuracy dropping off as you reach your 30s. To account for the effects of aging and body fat differences between the sexes, Halls suggests that the cutoff for being overweight should be 2 BMI points higher for men and increase with age. He also points out that, unlike men, women's BMIs are not stable across different heights. As it is natural for shorter women over the age of 30 to have higher BMIs, Halls suggests that the cutoff for being overweight should be higher for shorter women.