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Here is why BMI is BS

Updated: Jan 19, 2023

As far back as our memory serves us, the conversation about the supposedly mystical number that determines our overall health condition, AKA Body Mass Index or BMI, was almost always part of a doctor’s appointment. If this doesn’t make you dread your medical visits, I don’t know what will.

Before digging more deeply into why BMI is total BS, did you know that it was actually created by Lamber Adolph Jacque Quetelet, a Belgian mathematician in the 1800s? He used it as a tool to measure the average weight of an all-men, all-white population. Yup, you heard that right! Neither females nor other ethnicities were included in his calculations, proving that the group on which it was based isn’t representative of the diverse populations it’s currently used on in any way. Quetelet himself even stated that BMI was NOT appropriate for use on the individual level.

Despite being created almost 200 years ago, it’s still commonly used as a primary indicator of health by various healthcare providers. So, if you think it’s weird that we’re still relying on an out-of-date assessment tool that wasn’t even created by a medical expert or health researcher, you’re absolutely right.

The MANY problems with BMI

Now to the hot stuff! Other than the fact that it was created by a mathematician, here are 4 major reasons why BMI is total BS:

1. BMI doesn’t take into consideration factors other than weight and height.

The equation supposedly estimates the percentage of body fat by dividing your weight (in kg) by your squared height (in m). That’s it! It doesn't take into account differences in other factors such as age, sex, genetics, or ethnicity. It was created by white men, for white men and research suggests that it is even less accurate for people of colour. Different races & ethnicities have different body compositions, and two people with the same weight might not look similar due to genetic factors. Using a one-size-fits-all assessment tool like the BMI isn't appropriate for everyone and can even lead to the misdiagnosis and inappropriate treatment plans.

2. BMI is not an indicator of health.

There are several other aspects that affect a person's overall health and well-being which are frequently disregarded because of weight. People who have a "normal" BMI may be unaware of an underlying health condition because their weight is perceived as "healthy". On the other hand, just because someone falls under the "overweight" or "obese" category according to their BMI doesn't necessarily mean that they have health issues. They might in fact be healthier than those with a "normal" BMI. These weight biases can perpetuate a cycle of weight-based discrimination leading to unequal access to healthcare and it might affect people of all sizes. This is why it's crucial for practitioners to evaluate their patients’ bloodwork, nutrition, food security, sleep, stress, habits, etc. to assess their health.

3. BMI cut-offs are made up.

Did you know that in July 1998, the National Institutes of Health changed the cut-off levels and what it means to be "overweight", lowering the normal/overweight cut off from 27.8 (men) and 27.3 (women) to a BMI of 25. This meant that suddenly about 29 million Americans who had been considered “normal” weight became "overweight" even though they hadn’t gained an ounce.⁠ This change was done despite researchers advocating for the BMI cut-offs to be INCREASED (not decreased). Critics of this change noted that those guidelines were drafted in part by the International Obesity Task Force, whose two principal funders were companies making weight loss drugs.

4. BMI cut-offs prevent people from getting the care they need

But the biggest issue with the BMI is that it is used to deny people life saving, gender affirming care, or reproductive care. Physicians worried about liability use the BMI as a screening tool to deny treatments and surgeries to people in larger bodies. They often require people to lose a significant amount of weight before they can access the care that they so desperately need. This can result in undesirable practices such as restrictive dieting, disordered eating, and weight cycling which could lead to serious medical conditions.

So in short, I hate the BMI. Diet culture makes us believe that we have to shrink our bodies in order to reach a certain BMI range, and we are actually congratulated and praised when we do so. Health can be achieved at ANY size and it looks different on EVERY PERSON. Rather than relying on the BMI, shift your focus to how you feel, your energy levels, and the quality of your relationships with food and your body.

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