Body Mass Index: Do You Know Yours?

Add this number to your need-to-know file: your body mass index.

Just like your blood pressure reading or cholesterol level, your body mass index (BMI) has an impact on your risk of many health problems, including heart disease, type 2 diabetes and some cancers. With a lower BMI, you typically have lower blood pressure readings and lower levels of blood sugar and cholesterol.

Mayo Clinic's Warren Thompson, M.D., answers questions about BMI in the February issue of Mayo Clinic Women’s HealthSource.

What is it? Body mass index is the most common measure used for defining obesity. You can calculate it by dividing your weight in pounds by height in inches squared and then multiplying this answer by 703. A BMI of 18.5 to 24.9 is considered the healthiest. People with a BMI between 25 and 29.9 are considered overweight. BMI numbers over 30 indicate obesity.

What about other measures? Both waist circumference and waist-to-hip ratio provide a measure of central obesity. People who have more weight in the abdomen and waist - central obesity - seem to have higher risk of obesity-related health problems than those whose weight is concentrated in the buttocks and thighs. Women whose waist-circumference measurement is 35 inches or more may be at greater risk of health problems than are those who have smaller waists.

BMI and these other measures are useful because they provide information that’s independent of each other. With a normal BMI, you could still be at increased risk if you had a high waist-circumference measurement. The highest risk is for people with both a high BMI and high waist circumference.

Why should women discuss BMI and other measurements with their doctor? Weight loss can be a touchy subject because some people tend to feel guilty and ashamed about their weight. Objective measures are a starting point for a discussion on weight loss and health goals - with a focus on looking forward.