The time has come to dump BMI.
BMI, also known as Body Mass Index, is probably the most well-known health measurement after height and weight. It’s a simple mathematical ratio of your weight in kilograms divided by your height in meters squared, and it’s commonly used by physicians, insurance companies, and regular people around the world to determine if a person is considered overweight or obese.
However, relying on BMI as a health indicator at the individual level is not only unhelpful; it can also be downright misleading and even mask your risk for serious health issues.
This is because BMI leaves you in the dark regarding your visceral fat content.
Visceral fat is a special kind of fat that is hidden deep inside your abdomen and surrounds your inner organs. Everyone has some. Unlike surface level (subcutaneous) fat, it’s not easy to gauge how much visceral fat someone has just by looking at them. That’s because visceral fat is hidden away in the abdominal cavity, in between your organs.
BMI will not and cannot detect any kind of fat, including visceral fat. If you rely on BMI as your primary tool to assess weight, you may have significant amounts of visceral fat and not know it.
Although surface level fat is what most people (and the media) focus on, visceral fat is actually the worse of the two. That’s because visceral fat acts like another, living organ inside your body.
Unlike the organs that you were born with that sustain life, visceral fat actively works from the inside out to sabotage those organs and ruin your bodily functions.
According to Harvard University, visceral fat secretes a number of hormones and chemicals. One group of these chemicals is called cytokines. Cytokines play an important role in the human body, but increased levels of cytokines due to excess visceral fat can be problematic. Once cytokines enter the liver, they influence the production of blood lipids, which has been linked to higher cholesterol and insulin resistance. This can lead to Type 2 diabetes.
Type 2 diabetes is typically associated with people who are overweight or obese, and individuals whose BMIs above the normal range (18.5-24.9) are said to be at a significantly greater health risk. However, BMI can misrepresent people who are either near or slightly over the 24.99 mark.
Depending on lifestyle factors, some people can have large amounts of visceral fat, yet a “normal” BMI because they don’t have much skeletal muscle. Due to the trend towards sedentary lifestyles, this is becoming more and more common.
Excess visceral fat is unnecessary fat and develops as a result of having a caloric surplus. Unsurprisingly, visceral fat develops as a result of adopting unhealthy lifestyle habits. Some of these factors include:
For people living sedentary lifestyles, it is quite easy to pick up several of these unhealthy habits. Over time, these habits will lead increased amounts of body fat, including visceral fat.
After being calculated, BMI scores are compared against the BMI ranges set by the World Health Organization or another medical body (like the CDC), and if your BMI falls between 18.5 – 24.9, you are said to be “normal” weight. Using the formula, anyone with a calculator and a BMI chart can tell you if you’re overweight in a matter of seconds.
Unfortunately, that’s where problems can begin. That’s because BMI was never intended to be used to measure individuals at all.
The World Health Organization, whose BMI ranges are often cited in fitness centers and health clinics, doesn’t try to hide the fact that BMI has limitations (emphasis added):
The BMI provides the most useful population-level measure of overweight and obesity, as it is the same for both sexes and for all ages of adults. However, it should be considered as a rough guide because it may not correspond to the same body fat percentage in different individuals.
Despite this clear message, many doctors, physicians, and regular people continue to use BMI as a diagnostic tool simply out of convenience.
Fortunately, a growing number of people are beginning to take notice. BMI’s usefulness as a reliable weight index for individuals has been repeatedly debunked by a variety of sources by pointing to flaws such as:
Recall that BMI is determined by the simple division of weight and height. Weight is determined by standing on a scale; height is determined by measuring tape. These are very basic measurements. BMI cannot determine if you are lean, overweight, or somewhere in between. It’s all just raw numbers with BMI.
People with healthy BMIs are sometimes overheard as saying things like: “My metabolism is really high,” “My body just burns fat naturally; I’m lucky,” or “I guess I just have good genes.” You probably know the type.
However: No one should expect to eat a diet high in calories and saturated fat, totally ignore exercise, and expect to be healthy their entire life.
How can you figure out if you’re at risk for having large amounts of visceral fat? Don’t stand on the scale; that won’t help. Here are some options.
According to the Mayo Clinic, using a measuring tape to measure your waistline is a fairly good way to estimate your visceral fat content. If your waist measures 35 inches (women) or 40 inches (men), you may be carrying too much visceral fat.
The most precise method of determining the amount of visceral fat deposits is by taking a medical-grade exam such as a computerized tomography (CT) scan, an MRI, or a DEXA test.
These require access to a facility that has them, and although they are accurate, they might not be the most accessible or affordable option.
Another way to measure how much visceral fat you may be carrying is to get a body composition test performed. Body composition does not rely on BMI and attempts to determine what your body is made of, such as your fat and fat-free masses.
There are several ways and methods for testing body composition. Body composition analysis tests determine body fat percentage and accounts for visceral and subcutaneous fat.
One of the most well-known and popular method is to use skinfold calipers. These pinch your fat that lies under your skin (subcutaneous fat), and from those results, your total body fat percentage, of which your visceral fat comprises a part, is calculated with equations.
A second option is medical-grade BIA body composition testing. These tests measure the resistance experienced by an electric current as it travels through your body to determine your body fat percentage, which includes your visceral fat. Some advanced BIA devices are able to report visceral fat content, although you would need to ensure that the device you are using has this capability.
Knowing your body composition will give you a much better idea about your amount of visceral fat than BMI can. If your weight and/or BMI is considered “normal,” but your body composition test reveals you have a high body fat percentage (as with people who are skinny fat), you might want to consider making some lifestyle changes to reduce your risk of getting potentially serious diseases in the future.
Hopefully this clears things up for you – don’t rely on BMI to measure yourself!
The good news is, if you exercise, eat well, and live a generally healthy lifestyle, you’re going to avoid gaining too much visceral fat as the result of the good choices you’re making, and you won’t need to worry about BMI too much.
But if you don’t exercise, don’t eat well, yet have a “normal” weight and BMI, don’t let your guard down! Your BMI may be misleading you. Body composition testing will always give you much more information than your BMI ever will, and can give you a much better picture of everything that makes up your weight, including your visceral fat.