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BMI: What’s in a Number? 

Knowing your body mass index can help you reach your weight goal.

Is the weigh-in at your doctor visit the most agonizing part of your appointment? Do you weigh yourself at home monthly, weekly or (gasp) daily? However you track your weight, you might not be getting a complete picture of your health based solely off the number on the scale. But calculating your body mass index (BMI) can give you a better idea of where you stand. 

To calculate your BMI, first weigh yourself in pounds and measure your height in inches. Divide your weight in pounds by your height in inches squared. Then, multiply by 703. Or, use an online BMI calculator like the one here

Reading the Numbers

Once you’ve calculated your BMI, you’ll want to find out what it means. The classifications for adult BMI are:

  • Below 18.5—underweight
  • 18.5 to 24.9—normal
  • 25 to 29.9—overweight
  • 30 and above—obese

Having a BMI of 25 or higher puts you at risk for certain diseases and conditions, including hypertension, high cholesterol, type 2 diabetes, heart disease, stroke, gallbladder disease, osteoarthritis, sleep apnea and some cancers.

The Bigger Picture

BMI measurement isn’t perfect and it has limitations. Just as weight alone doesn’t take height into account, BMI doesn’t take into account your body shape and build. For instance, two people of the same height and weight can have differing amounts of body fat. Women tend to have higher percentages of body fat than men. And older adults tend to have higher percentages of body fat than younger people. Athletes may have high BMIs because the calculation doesn’t account for muscle mass that weighs more than fat. Race and ethnicity also play roles in determining healthy build. Another tool in assessing body fat is waist circumference. Disease risk is increased in women with waists greater than 35 inches and in men with waists greater than 40 inches.

Of course, body size isn’t always indicative of fitness. An overweight person can still be considered fit just as someone of normal weight could be unhealthy. Talk to your doctor about your weight and fitness level to determine what’s healthy for you.