What is BMI and Why Does it Matter?

If you've ever talked with a health care provider about weight loss, you've probably heard the term BMI. BMI, or Body Mass Index, is one of the most commonly used tools for evaluating weight and determining whether someone may be at increased risk for obesity-related health conditions. But despite its widespread use, many people don't know what BMI actually measures, how it's calculated or what it means for their health.

Let's break it down.

What Is BMI?

BMI stands for Body Mass Index. It's a simple calculation that compares your height to your weight. The result is a number that helps healthcare providers estimate whether you're within a healthy weight range for your height.

It's important to understand that BMI isn't a direct measurement of body fat. Instead, it's a screening tool that helps identify people who may be at increased risk for health conditions related to excess weight.

Because it's easy to calculate and widely accepted, BMI has become the standard measurement used in many areas of healthcare, including bariatric surgery.

When is a BMI Considered Obese?

In general, a BMI of:

• 18.5 to 24.9 is considered healthy
• 25 to 29.9 is considered overweight
• 30 or higher is considered obese

When considering weight loss surgery, BMI is often one of the factors used to determine eligibility. Many insurance plans consider patients eligible for bariatric surgery if they have:

• A BMI of 40 or higher, regardless of other health conditions
• A BMI of 35 or higher with a significant obesity-related condition, which may include:
  • Type 2 diabetes
  • Sleep apnea
  • High blood pressure
  • Coronary artery disease
  • Fatty liver disease

Every patient is different, so eligibility is based on more than a single number. However, BMI remains one of the primary tools used in the evaluation process.

Is BMI a Perfect Measurement?

No. BMI is useful, but it has limitations.

One of the biggest criticisms of BMI is that it doesn't differentiate between fat and muscle. Since muscle weighs more than fat, some people with significant muscle mass can have a high BMI even though they are very healthy.

Consider a professional bodybuilder. Their weight compared to their height may place them in the obese category according to BMI calculations. However, if you saw that person, you likely wouldn't consider them obese. They may have extremely low body fat and excellent physical fitness.

That's why health care providers don't rely on BMI alone when assessing a patient's overall health.

Why Do We Still Use BMI?

If BMI has limitations, why does health care continue to use it? Simply put, it's the best standardized tool we currently have for evaluating large populations and identifying people who may benefit from additional medical evaluation or treatment.

BMI provides a consistent starting point for conversations about weight-related health risks. It helps health care providers identify patients who may be at increased risk for conditions such as diabetes, heart disease, sleep apnea and other obesity-related illnesses.

While it's not perfect, it's a useful tool when combined with a comprehensive evaluation of a patient's overall health,

Improving Your BMI

Since BMI is based on height and weight, lowering your weight will reduce your BMI. For some people, lifestyle changes such as improved nutrition, increased physical activity and behavior modification can lead to meaningful weight loss and improved health outcomes.

For others, obesity may be more complex and influenced by genetics, hormones, metabolism and other factors that make long-term weight loss difficult to achieve through lifestyle changes alone. In those situations, additional treatments such as weight management programs, medications or bariatric surgery may be appropriate options.

The Bigger Picture

Although BMI is an important measurement, it shouldn't define how you view your health or your success.
A number on a chart is only one piece of the story. The goal isn't simply to lower a number. The goal is to improve your health, reduce your risk of chronic disease and help you live a longer, healthier life.

If you're concerned about your weight or wondering whether you might be a candidate for bariatric surgery, talk with a health care provider who can help you understand your options and develop a plan that's right for you.