Among all the numbers your doctor takes at your appointment — like blood pressure, cholesterol, or body temperature — your body mass index (BMI) is likely the one to stick in your memory. Maybe your doctor told you that yours means you fall into the overweight or obese category, for example, and they recommended bringing your number down. Or maybe they told you that your BMI is in the normal range, which suggests that you’re at a healthy weight, or too low, meaning you’re considered underweight.
BMI can be a sensitive topic — and maybe you don’t care to pay it any mind. Some medical professionals support that choice. “Unfortunately, there is no perfect tool [to measure one’s health],” says Anisha Abraham, MD, interim chief of the division of adolescent and young adult medicine at Children’s National Hospital in Silver Spring, Maryland. Instead, there are several measurement tools, such as blood pressure, BMI, and blood sugar, that tell us different things but are pieces of a larger puzzle, she says.
Body fat percentage is another one. Frank Contacessa, MD, an internist with Northwell Health Physician Partners in Armonk, New York, says that it’s a better factor to consider in a holistic health assessment, but it’s more difficult to measure than BMI.
All the same, you may be wondering what your BMI suggests about your present and future health — and how much stock should you put your number?
Here’s an overview of how and why BMI is used, and what yours may mean.
To calculate your BMI, take your weight in kilograms and divide it by your height in meters squared. Alternatively, take your height in inches squared, divide that by your weight in pounds, and multiply by 703.
You can avoid doing manual math by plugging your stats into an online calculator, like the one from the Centers for Disease Control and Prevention (CDC). To see how your weight stacks up against your height, you can use the body mass index table from the National Heart, Lung, and Blood Institute (PDF).
Here are the ranges and how the CDC describes each:
- BMI below 18.5 is underweight (too low).
- BMI 18.5 to 24.9 is normal weight (just right).
- BMI 25 to 29.9 is overweight (high).
- BMI 30 and higher indicates obesity (very high).
How BMI Is Limited
The flaws of using BMI as a measure of health are well documented.
Focusing Too Much on BMI, and Weight in General, Can Be Harmful to Emotional Wellness
Something to keep in mind is that a focus on BMI in the doctor’s office or in your daily life may increase weight stigma and harm your mental health. “Overfocusing on BMI can affect self-esteem and emotional wellness,” Dr. Abraham says. “For example, I have had patients who developed body image and eating disorders as a result of being told that they had a high BMI and needed to change their weight.”
Just because you’re considered overweight or obese according to your BMI doesn’t necessarily mean you’re unhealthy — your healthy eating and exercising habits mean more, despite what the scale (or BMI calculator) says.
Rather than shoot for a specific BMI, what may be most important is maintaining — or starting — healthy habits.
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