What is BMI?

BMI or body mass index is a measurement of an individual’s weight in regards to height. In other words, it is a ratio of weight to height. It is calculated by dividing weight in kg by height in meters squared. BMI is the most commonly used measurement to determine an individual’s health status. It is used to categorize people as underweight, normal/healthy weight, overweight, & obese. In a health care setting, an individual’s BMI is used to determine treatment plans, conversation topics between caregiver & patient, what specialists see a patient, health insurance rates, and more. So, is BMI accurate?

Is BMI Accurate? – Five Reasons Why BMI Should be Kicked to the Curb

1. An individual’s health status is determined by decimal points

The fact that an individual is classified as healthy at a BMI of 24.9 but is unhealthy at a BMI of 25 is pretty crazy. Also, an individual might be classified as moderately unhealthy at a BMI of 29.9 but is automatically classified as extremely unhealthy at a BMI of 30. To put this into perspective, I will use myself as an example. I am 5’ 2.5” (yes, that half-inch counts! lol). Let’s say I weigh 138 lbs…that would put me at a BMI of 24.8 which would classify me as healthy. However, let’s say I weigh 139 lbs… that would put me at a BMI of 25.0 which classifies me as overweight. This means that if someone was basing my health status off of my BMI, I would suddenly be considered unhealthy because of one pound, one pound! That’s pretty crazy if you ask me.

2. BMI is outdated and was created for non-health purposes

BMI was created in the 19th century by Lambert Adolphe Jacques Quetelet, a Belgian mathematician. He was not educated in health sciences nor was he a medical doctor, physician, or any other health care professional. BMI was developed to measure the degree of obesity within a population in order to assist the government in allocating resources. It was to be used to generalize the weight of a population, not to determine characteristics of an individual. Also, the research used to develop BMI was based only on male populations.

*Quetelet requested that his BMI formula would not be used to determine an individual’s health status or level of fat.*

So why did we even start using BMI in health care and why are we still using it?

3. It uses weight as a determinant of health

The BMI formula requires an individual’s weight for it to be used. Using weight as a determinant of health is not only inaccurate but is harmful. Currently, there is a multitude of research out there that focuses on pursuing health through nourishing food and physical activity instead of through weight loss. It is being seen time and time again that weight loss is not sustainable in the long term nor does it improve long term health status. Research studies are showing that the weight loss approach to health should be abandoned and that non-diet approaches to health such as Health at Every Size (HAES) and Intuitive Eating (IE) should be used instead if overall health and wellness is the ultimate goal.

4. It doesn’t take into consideration muscle mass, bone size, gender, ethnicity, disease states, age, activity level, etc.

If someone is going to determine health status by BMI, there are several other reasons why BMI is inaccurate, regardless of whether or not weight is thought to influence health. BMI doesn’t consider muscle mass, bone size, gender, ethnicity, disease states, age, activity level, or anything else that impacts health status. By not considering these additional factors, thousands and thousands of people will be wrongly characterized. Not only does this falsely identify an individual as healthy or unhealthy but it leads to discouragement, discrimination, and stigma.  

5. It’s a cop-out

Put bluntly, it is a lazy way to determine someone’s health status. Health is a complex concept that cannot be determined by calculating the ratio of weight to height. There are so many complicated pieces to the puzzle of health and weight isn’t one of them. Health care professionals don’t always have the time or energy to examine the intricate details that influence an individual’s overall health status. These factors can include mental health, diet patterns, physical activity habits, genetics, environmental factors, socioeconomic status, and so much more. Instead of investigating these factors, health care professionals tend to look at BMI and create an action plan from it. In the end, this does a disservice to the individual seeking help and paying for health care services. 

So what do you think? Is BMI accurate?

Thanks for reading my thoughts!

Sincerely,

Rachel Beiler, MHS, RD, LDN

You have to nourish to flourish!