Body mass index or BMI is a calculation derived from a person's height and weight that usually correlates well with the amount of body fat a healthy person should have. It is used by doctors as a convenient screening measurement to identify individuals who might have an elevated risk of heart disease and other health problems associated with excess body fat.
Calculation
BMI can be determined by dividing your weight in pounds by height in inches squared. Multiply the result by a conversion factor of 703 to find your BMI. In the metric system, the equation for BMI is weight in kilograms divided by height in meters squared. Height is usually measured in centimeters, so first divide height in centimeters by 100 to obtain height in meters.
Results
Individuals with BMI measurements below 18.5 are considered underweight. Those with a BMI between 18.5 and 24.9 fall within the normal range. A BMI value of 25.0 to 29.9 places an individual in the overweight range, and those with a BMI greater than 30.0 are considered obese.
Other Risk Factors
BMI is just one tool that doctors use to screen people for possible health issues due to weight. You are also at an increased risk for heart disease and other conditions related to obesity if you have high blood pressure, elevated cholesterol, low HDL cholesterol, high levels of triglycerides, elevated blood glucose or diabetes. Additional risk factors include a family history of early-onset heart disease, physical inactivity and cigarette smoking.
Recommendations
Your health care provider should evaluate your health history, activity level and the risk factors above, in addition to BMI. For some individuals, BMI does not accurately reflect body fat composition and health. For example, very athletic individuals may have a high BMI due to dense muscle mass. If your BMI places you in the obese or overweight categories and you also have two or more risk factors, your doctor will probably recommend that you lose weight. Even a modest weight loss of 5 to 10 percent of your current weight will significantly decrease your risk of health complications. Discuss weight loss plans with you doctor to find one that is appropriate for you.
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