What is BMI? (And How Much Does It Matter?)

Contributed by: Meredith Presnell, APRN-CNP | Obesity Medicine

BMI—or Body Mass Index—is a simple calculation that shows the relationship between a person’s height and weight. While it’s a common measurement that helps to screen if a person is overweight, it does not always reflect how healthy a person is. There are other factors that your health provider looks at, including blood pressure, cholesterol, and glucose levels. It’s important to see your primary care provider to discuss your overall health as it relates to BMI.

The medical world is full of advanced statistical modeling, but BMI—or Body Mass Index—is a simple calculation. Any person can calculate their BMI by dividing their weight—in kilograms—by their height—in meters. Visit the National Institutes of Health BMI Calculator here.

BMI groups people into four categories:

Although health insurance plans use BMI as a tool to determine coverage of weight loss treatments like medication and bariatric surgery, BMI doesn’t always tell the complete story, according to Meredith Presnell, APRN-CNP, a provider at the MetroHealth Weight Loss Center.

“BMI is a good screening tool because it’s the only tool we have so far that is quick and easy,” says Presnell. “BMI doesn’t take into consideration a person’s body fat percentage, where excess weight is located on a person’s body, or the amount of muscle a person has.”

While screening for a person’s BMI is a way to start a conversation about weight, at the MetroHealth Weight Loss Surgery and Weight Management Center, we take a more complete view of a person’s health.

For instance, if someone carries excess weight around their abdomen—called central obesity—they are at higher risk for obesity-related diseases like heart disease and diabetes.

“BMI helps people get in the door to have a broader conversation about their health,” says Presnell. “Then, we can review other screenings like A1C, cholesterol and blood pressure. We treat obesity for health reasons: reducing risk of heart attack, stroke, fatty liver disease and diabetes.”

If a higher BMI has motivated you to contact the MetroHealth Weight Loss Center, it’s important to understand what will happen at your first appointment.

“Numbers don’t tell the whole story when it comes to obesity,” says Presnell. “We’re trying to achieve health and quality of life.”

One screening tool your provider may use is the Edmonton Obesity Staging System, which measures a person’s metabolic, physical, and psychological characteristics, versus using height and weight to calculate BMI.

“We have to get past the idea that obesity is a cosmetic thing—that we lose weight to look better,” says Presnell. “Obesity is a chronic disease process, and we treat obesity because it’s often the root problem of other diseases.”

“I’ve seen bodybuilders with 10% body fat, but a high BMI because of the amount of muscle they have,” says Presnell. “Numbers don’t tell the whole story.”

What does, says Presnell, are the overall health improvements she’s seen patients achieve.

“I’ve seen patient’s A1C levels drop, I’ve seen their fatty liver disease reverse, I’ve seen them be able to put their shoes on without getting out of breath,” says Presnell. “That’s the stuff that matters—not just the numbers you see on a scale.”