When I started my weight loss journey, I was overwhelmed by all of the data I was supposed to be tracking. Tasks like calculating macros and counting calories seemed to take over my days, and I wasn’t convinced that any of it was helping. Of course, the road to weight loss looks different for all of us. Some people swear by keto, while others shed pounds by simply adding a walk to their daily routine. My journey has involved a mixture of healthy eating and exercise — as most weight loss success stories do — but I had to wade through a ton of questionable advice to figure that out.
One number I’ve always been skeptical about is body mass index (aka BMI). As one of the key metrics for monitoring weight and health, the BMI chart is a fixture in almost every doctor’s office in America. It provides quantifiable measurements, which is why it’s generally considered the baseline for managing health conditions, especially those related to weight, like heart disease or type 2 diabetes.
But anyone who has struggled on their weight loss or weight gain journey knows that there are many factors involved in determining our weight. These factors go well beyond the ratio of body fat to height and may include genetics, ethnicity, family history, and a whole lot more. While BMI was a useful tool for providing health information in the past, there are several things to keep in mind when you measure your body weight and discuss weight loss options with your healthcare provider.
What is BMI?
Simply put, BMI value measures the level of body fat a person has based on their height and weight. The healthy BMI range varies more for children and adolescents, as they grow at different rates, but the range is consistent for adult BMI measurements. The BMI formula was introduced in the 19th century by a mathematician and sociologist named Lambert Adolphe Jacques Quetelet, and it was initially designed for use in larger population studies and to determine the rate of obesity in prosperous western regions. Since the 1980s, it’s been used by international organizations like the World Health Organization (WHO) as a standard for measuring obesity worldwide.
It works like this: Once your body mass index is measured based on height and weight, you’re categorized into one of four quadrants — underweight, normal weight, overweight, and obese. According to the guideline, the categorization can be used to provide more informed diagnoses and better healthcare support and guidance.
Can BMI be misleading?
Despite its ubiquity, the BMI index has faced criticism as a tool for measuring body fat and determining wellness. Here are just a few of the reasons that BMI can be misleading, and how you can adjust your healthcare plan to better fit your needs.
Population Data Versus Individual Data
While Quetelet may not have been a doctor, he was a statistician and sociologist, and he insisted that the data collected for different BMI categories was not an accurate representation of an individual person’s health and fitness. Rather, it was to be used as a method for analyzing population information and drawing conclusions about access to resources and health for a larger data pool. BMI accounts for height, which is an important factor when determining a healthy weight for an individual. That said, it fails to account for many other determining factors and influences that affect individual patients.
Muscle Mass, Body Composition & More
While the broader data collected on BMI may be useful in determining regional or national health trends, there are many places where the data can fall short for the individual. That’s because numerous factors determine obesity, and BMI doesn’t account for all of them. One of the most important factors healthcare professionals consider when looking for signs of obesity is waist circumference. That is because excessive abdominal fat can put individuals at higher risk of chronic health problems like type 2 diabetes and high blood pressure.
BMI doesn’t account for waist circumference or several other influencing factors that can significantly alter the number on the scale. Among these is muscle mass. Your muscle mass will change significantly based on your level of physical activity and diet, which can lead to an obese categorization, even when a person is otherwise in peak health. Bones are denser than both muscle and fat, which means healthy, strong bones can actually register a person’s body weight as higher, despite having no connection to body fat. The term body composition refers to the breakdown of weight from muscle, bone, and fat, versus looking at the overall weight of the body. Without a more nuanced perspective that accounts for all contributing factors, many individuals may be categorized as having high BMI for the wrong reasons, and others as having low BMI, reducing their access to essential health information.
Genetics and Family History
Recently, there have been many studies conducted on the correlation between genetics and obesity. While it’s difficult to draw a definitive conclusion about how obesity is passed down through generations, it’s clear that some connection exists. There is also evidence suggesting that early exposure to famine or food insecurity can affect how the body retains energy, leading to excess body fat. While this topic hasn’t been sufficiently explored, it points to broader influences on obesity and weight gain than simple calories in and calories out. BMI fails to account for both environmental impacts, such as genetics and where and how a person was raised.
The more scientists are able to explore this correlation between genetics, family history, and environment, the better we’ll be able to understand what causes obesity. This will allow us to create more comprehensive methods for losing body fat and reducing the risk of chronic conditions.
Another reason it’s important to take BMI with a grain of salt is because of the way that the study was conducted. The original index was used in Europe on a homogenous population. Specifically, data was collected almost exclusively on white patients, removing the possibility of insights based on ethnicity or family history. Applying data gleaned from an exclusively white population to Black patients and other patients of color doesn’t address variations between populations. For example, the BMI index doesn’t account for predisposition to specific allergies or conditions for certain ethnic groups. Rather than attempting to retrofit an incomplete data study from more than a century ago, we must create a more inclusive study of weight and health.
The BMI index sets up distinct quadrants for each of the four body quadrants — underweight, normal, overweight, and obese. A person can move between these four quadrants simply by losing or gaining a few pounds, as BMI is only measured to a tenth of a point. In truth, weight regularly fluctuates based on many influencing factors, among them environment, a recent meal, hydration levels, and medical conditions. To split the body weight distribution into four simple quadrants is to miss many of the important factors that determine weight and overall health. A better analysis of body facts would include bone density and muscle mass, level of physical activity, personal health information, a history of diseases or chronic conditions, and more.
Despite everything, the BMI index remains prolific because of its quantifiable capabilities for measuring health, which can be used to allocate resources, price insurance, and establish population resilience, among other things. But the quantifiable nature of BMI also means there is no room for interpretation or nuance, both of which are essential to understanding obesity and creating a plan for risk reduction. When it comes to a useful indicator of health, there are other tools and resources that can provide greater insight without the decimal point.
What’s it all mean?
The BMI calculator has long been used by institutions like the World Health Organization and the Centers for Disease Control (CDC) as a tool for measuring body fat percentage and related health risks and wellness conditions. But while BMI may have its place in the medical field, individual patients should keep outside factors and influences in mind when seeking care.
A tool designed for large group data collection that doesn’t incorporate factors like body composition, family history and genetics, ethnicity, gender, and more might not be the best health benchmark for individual patients. If you’re worried about your weight and how it might put you at risk for chronic diseases, speak to your doctor or healthcare provider about your concerns. They’ll work with you to create a personalized healthcare plan that accounts for your specific health and wellness needs.