Your body mass index (BMI) results from a formula used to estimate a healthy weight for you, based on your height. Being overweight or having a BMI that is too high can lead to major health problems, including type 2 diabetes, heart disease, high blood pressure, sleep apnea, arthritis, and varicose veins.

To calculate your BMI, start by multiplying your weight in pounds by 703. Divide the answer by your height in inches. Divide that result by your height in inches again. A woman or man who is 5 feet 4 inches (64 inches) tall and weighs 120 pounds has a BMI of 20.6: [(120 × 703) ÷ 64] ÷ 64 = 20.6.

There are five standard BMI categories. Someone with a BMI of below 18.5 is underweight, 18.5 to 24.9 is considered healthy, 25.0 to 29.9 qualifies as overweight, 30.0 to 39.9 is categorized as obese, and 40.0 or higher is considered morbidly obese. These ranges should not be used to assess the BMIs of children.

Your BMI is partially determined by heredity. People from different ethnic backgrounds tend to have different body fat distribution (they build up fat in different parts of their bodies) or body composition (proportions of bone, muscle, and fat). However, no matter what your genetic predisposition, you can have a healthy body and keep your weight in control by eating a balanced, reduced-calorie diet and exercising. Simple forms of exercise, such as walking for 20 minutes daily, can have positive effects on your health and help control your BMI.

ADDITIONAL FACTS

  1. It’s estimated that 300,000 deaths a year in the United States could be prevented if everyone maintained a healthy BMI.
  2. Studies show that the average age of a first heart attack for people with BMIs of 18.5 and under is 75. For people with BMIs of 40 and over, the average age is 59.
  3. Sometimes your BMI is not the best way to tell whether you need to lose weight. For example, very muscular individuals may have higher BMIs, because muscle weighs more than fat. And people over 65 may benefit from having a BMI between 25 and 27, rather than under 25.