Why BMI is an ineffective measurement for obesity

Guest Post by Shaun DMello (see bio at the end)

Body Mass Index (BMI) has long been the standard measurement for obesity and health, but this may be a flawed approach. In theory, BMI is a simple tool to gauge someone’s body fat content, taking into account their height and weight. Individuals are then categorized as healthy (body weight) or obese. Unfortunately, BMI is ineffective as it oversimplifies data, looking only at weight and height, while ignoring or failing to differentiate between other parameters concerning obesity and health. An effective obesity indicator should help to identify any excess fat that poses a health risk; something that BMI fails to do.   

The Many Failings of Body Mass Index or BMI

Cannot distinguish between types of fat

Among its many limitations, most notable is BMI’s inability to distinguish between the different types of fat. This is actually an important indicator of health risks, as different types of fat can have different metabolic health effects. This flaw was highlighted in a study published in the journal Nature Research. Abdominal or belly fat, which is classified as visceral fat, is known to increase the risk of conditions like diabetes and heart disease as it disrupts hormonal balance and metabolic functions. 

The failure of BMI to consider the location of body fat means that thin adults with high visceral fat content may be considered healthy, despite their high risk of developing disorders linked to obesity and weight gain.

Cannot distinguish between muscle weight, bone density, and fat

This is a huge flaw that can lead to significant misclassifications. Scientists have long warned that BMI is ineffective and imprecise as it does not distinguish between muscle mass and body fat. Muscle mass is actually heavier than body fat because of its high density. This means that a muscular and toned athlete could be misidentified as overweight or obese, while a moderately overweight individual may not be recognized as such.

To put it in perspective, consider this. A 200lbs MMA fighter who stands 6 feet tall would have the same BMI measurement as a sedentary adult with the same height and body weight. That’s clearly inaccurate, as much of the MMA fighter’s weight could be linked to muscle mass, which is not the case with the sedentary adult. This failure to distinguish between weight from different sources also means that weight differences from bone density and fluid go unaccounted.

BMI exaggerates thinness in short people and fatness in tall people

As should already be evident, BMI can lead to misclassifications that have real consequences – people trying to lose weight when they don’t need to and others being complacent about their diet and lifestyle choices because BMI readings (incorrectly) tell them that their body weight is healthy. As pointed out by some experts, the BMI formula divides weight by too much in those with a short stature, while it’s inadequate in tall individuals. As a consequence, individuals on the shorter side tend to think they’re healthier than they really are, while taller individuals mistakenly believe that they are overweight.

Proven Inconsistencies

A study published in the International Journal of Obesity underscores the impact of BMI’s poor efficacy as an obesity measurement tool. By looking at a range of accepted health metrics, such as cholesterol levels, blood pressure, and inflammatory markers, as well as BMI measurements, the researchers were able to make some observations. They found that 47% of those classified as overweight and 29% as obese were in fact healthy. At the same time, 31% of those classified as having healthy weight were found to be at risk of disorders linked to obesity.

Let’s face it. BMI is going to be around for a while, whether we like it or not. It’s an extremely easy tool to use and in our ‘self-help’ era, simplicity is everything. While we do use it however, it’s important to keep in mind that BMI alone is a poor measure of obesity and health risks. There is also growing evidence to show that waist-to-height ratio is a far better predictor of health status as compared to BMI. Of course, for any meaningful change in attitudes and approaches, we need changes in public health policy and within the community of health care providers itself.

Author Bio:

Shaun DMello is a prolific writer who has worked with a wide range of health and wellness brands for over a decade. His main areas of expertise are nutrition, fitness, natural medicine, public health, and health care technology, but he is most passionate about healthy lifestyle as he has struggled with type2 diabetes. When he’s not writing, you can find him reading a good book, curled up on a recliner, jostling for space with his four cats.