Your Body Mass Index

The human body is comprised of water, fat, protein, carbohydrate and various vitamins and minerals. If you have too much fat -particularly if you are carrying a lot of it at your waist line- then you're at higher risk for health problems such as high blood pressure, high blood cholesterol, heart attack and diabetes.

Body mass index (BMI) is a measure of body fat based on height and weight that applies to both adult men and women. BMI provides a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health problems. BMI does not measure body fat directly, but research has shown that BMI correlates to direct measures of body fat. BMI can be considered an alternative for direct measures of body fat. Additionally, BMI is an inexpensive and easy-to-perform method of screening for weight categories that may lead to health problems.

Calculation of BMI

The calculation of BMI is based on the following formula (shown in pounds and inches):

BMI Formula Calculation Formula: weight (lb) / [height (in)]2 x 703 Calculation: [weight (lb) / height (in) / height (in)] x 703 Calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703. Example: Weight = 150 lbs, Height = 5'5" (65") Calculation: [150 ÷ (65)2] x 703 = 24.96

Interpretation of BMI

For adults 20 years old and older, BMI is interpreted using standard weight status categories that are the same for all ages and for both men and women.

• BMI values less than 18.5 are considered underweight.
• BMI values from 18.5 to 24.9 are healthy.
• Overweight is defined as a body mass index of 25.0 to less than 30.0. A BMI of about 25 kg/m2 corresponds to about 10 percent over ideal body weight. People with BMIs in this range have an increased risk of heart and blood vessel disease.
• Obesity is defined as a BMI of 30.0 or greater (based on NIH guidelines) -- about 30 pounds or more overweight. People with BMIs of 30 or more are at higher risk of cardiovascular disease.
• Extreme obesity is defined as a BMI of 40 or greater.

Is BMI a Reliable Indicator of Body Fat?

The correlation between the BMI number and body fatness is fairly strong, although there are some variations including:

• At the same BMI, women tend to have more body fat than men.
• At the same BMI, older people, on average, tend to have more body fat than younger adults.
• Highly trained athletes may have a high BMI because of increased muscularity rather than increased body fatness.