Body mass index (BMI) has long been a common tool for estimating a person’s relative weight status based on a simple height to weight ratio. It’s easy to calculate, widely accessible and often used to categorize individuals into weight categories that range from underweight to obesity.
For decades, BMI has also served as a means for assessing disease risk, particularly those related to excess weight, such as cardiovascular disease and Type 2 diabetes.
Now, BMI is also used to assess whether someone is a candidate for GLP-1 drugs like Ozempic or Wegovy for weight loss.
[READ: Ozempic for Weight Loss: Side Effects and Safety]
What Is BMI?
BMI was originally created in the 1800s by a Belgian astronomer who was helping design a population census. When the formula was originally created, it was not intended to be used to assess someone’s individual health, but instead was intended to paint a picture of the average size of a large population.
For this reason, BMI often fails to paint an accurate picture of an individual’s health. For example, a professional football player may be classified as having overweight or obesity by the BMI scale, but their weight is mostly made of muscle mass, not fat mass.
As science evolves, and with the advent of new therapies like GLP-1 receptor agonists for weight loss, our understanding of what BMI can and can’t tell us about health must change.
As a starting point, you can calculate your BMI with the BMI calculator below and check it with the BMI chart.
Enter your height and weight, click “calculate,” then check your calculated BMI with the table to determine which category you’re in.
What BMI Still Does Well
Despite its well-documented limitations, BMI remains a useful initial screening tool, especially in public health settings where simple and scalable measures are needed to evaluate the collective health status of large populations. At an individual level, BMI can serve as a starting point for identifying potential health risks and prompting deeper evaluations.
Importantly, BMI also remains a key criterion for determining eligibility for certain medical treatments, including GLP-1 medications like semaglutide (Ozempic, Wegovy) and tirzepatide (Zepbound, Mounjaro). These medications are currently approved by the U.S. Food and Drug Administration (FDA) for individuals with:
— A BMI of 30 or higher (classified as obesity)
— A BMI of 27 or higher (classified as overweight) with at least one weight-related health condition, such as hypertension, Type 2 diabetes or dyslipidemia, a condition marked by abnormally high or low levels of fats in the blood, including cholesterol and triglycerides.
[READ: Zepbound for Weight Loss]
BMI and GLP-1 Medications
As promising as GLP-1 medications are, relying solely on BMI to guide their use poses real concerns.
First, not all weight is the same. BMI does not distinguish between muscle mass and fat mass. A person who is very muscular might qualify for medication despite being metabolically healthy, while another with high visceral fat (a dangerous type of fat that accumulates around the internal organs) but a “normal” BMI might be overlooked.
GLP-1s help with weight loss, but they also influence other health factors like blood sugar regulation and inflammation. Thus, someone with a lower BMI but high metabolic risk may still benefit from treatment, even if they don’t technically qualify based on weight alone.
Finally, as people lose weight with GLP-1s, BMI naturally drops, but that doesn’t always equate to better health if lean muscle is lost in the process. This makes ongoing assessment of body composition and physical function essential components of effective long-term care.
If you’re considering or currently using a GLP-1 medication, BMI may have been your ticket in, but it shouldn’t be the only measure guiding your health journey. Work with your health care team to:
— Monitor muscle mass and physical function alongside weight loss.
— Incorporate resistance training and protein intake to preserve lean mass.
— Keep track of metabolic health markers, not just your BMI score.
Likewise, health and fitness professionals should be prepared to support GLP-1 users with personalized exercise and nutrition strategies that prioritize strength, functionality and overall wellness, not just weight reduction.
[READ: Exercising on GLP-1s: How to Stay Safe and Healthy]
BMI Alternatives
To truly optimize health outcomes, whether someone is on GLP-1 therapy or not, we must consider a more nuanced set of indicators:
— Waist circumference and weight-to-height ratio. These measures give insight into visceral fat, a more dangerous type of fat than subcutaneous fat (fat located just beneath the skin).
— Body composition analysis. This analysis differentiates fat mass from lean mass and helps guide fitness or clinical interventions more effectively.
— Metabolic markers. Blood pressure, cholesterol, glucose and inflammatory markers are better predictors of health risk than weight alone.
— Functional fitness and strength assessments. This is especially important when weight is lost quickly, to ensure that physical capacity and quality of life are maintained or improved.
[READ: 15 Best Ways to Lose Belly Fat and Be Healthy]
Final Thoughts
The true value of BMI lies in its simplicity, not its precision.
BMI continues to offer value as a simple screening tool, particularly when used to initiate treatment or highlight potential health risks. However, its limitations are even more apparent in an era where precision health and individualized medicine are gaining ground. Health isn’t a number, it’s a complex interplay of biology, behavior and lifestyle, and our tools for measuring it should reflect that complexity.
Whether you’re using a GLP-1 medication, considering one or simply trying to take better care of your health, know this: Your BMI may start the conversation, but it should never be the final word.
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What Is BMI: Body Mass Index Explained originally appeared on usnews.com
