I have a running list of things that our current healthcare system desperately needs to overhaul, and Body Mass Index also known as BMI is in the top five. Let me break it down starting at the beginning.
BMI was developed by a Belgian statistician (not a doctor or anyone with a clue on how the human body works) in the 1830s. His goal for this mathematical equation - weight in kilograms divided by the square of height in meters - had nothing to do with measuring individual health or diagnosing obesity but rather it was a test to find the average, European, white male. It wasn't until the 1970s - the beginning of the obesity epidemic in America - when a dietician and his group of buddies conducted a poorly executed study (all men with an overwhelming majority of those men studied being of European decent) that promoted BMI as the quickest screen for obesity. It caught on like wildfire because it was convenient and the math was so easy a third grader could do it. Almost two hundred years later, it remains the most common index used in a medical setting to assess various disease risks and prescribe the uber popular weight loss drugs like Ozempic and Wegovy to adults and children as young as 12-years-old.
Unless you're a white man from the early 19th century with a goal of being average, BMI is not the assessment for you. It doesn't take into account your gender, your ethnicity, body composition or age. It can't tell your body fat or muscle mass - the actual, critical pieces of information you need to determine individual health outcomes.
Muscle
Most professional and elite athletes and their coaches have known BMI does not determine the strength or health of an athlete because it doesn't distinguish muscle mass and bone density from fat specifically abdominal fat. Muscle is denser than fat, but it also takes up less room in your body than adipose tissue. Muscle makes you look lean and toned even though the number on the scale is higher. Skinny, fat people are real.
Using the current index, most elite athletes are considered overweight, but they are also winning the longevity race by significant margins compared to the rest of us. Why? Muscle is the well-known currency of healthspan and the top predictor of age-related, chronic disease.
Fat
In peer-reviewed medical studies, BMI doesn't stand up when it comes to positive health outcomes. In fact, the study linked below specifically states in the first sentence of the first paragraph, "Obesity, as defined by BMI, hasn't been consistently associated with higher mortality." Another study found a higher BMI in the 25-35 kg/m2 range is optimal for health in older populations. Older adults above and below 25-35 kg/m2 (BMI ranges: <25 = normal; >35 = morbidly obese/Class III) are at a higher risk for malnutrition, falls, walking and mobilization disorders, reduced muscle strength and decreased functional capacity.
Fat matters but what's more important is where that fat is distributed in your body. If it's hanging around your midsection and cozying up next to your vital organs, you have a problem. Abdominal fat is directly linked to the silent killers - cardiovascular disease, insulin resistance, metabolic dysfunction and disease. If you're a curvy black or Hispanic girl with hips and a butt, that is the healthy version of you. Men and women have distinguishable bodies. We naturally hold and carry fat differently because of our hormones and how our body was designed to function. Body types also vary dramatically between ethnicities. This is the glaring problem with BMI and a huge factor in the inequalities in healthcare. The first thing you do at a doctor's office is step on a scale. If you're a female, especially if you are an ethnic female, you are immediately labeled as "unhealthy" because you don't fit in a centuries old box of the average white guy. Shame is not exactly the best way to start an appointment or a relationship with a healthcare provider. Not to mention, most of us would have to resort to very unhealthy, unsafe practices to reach that impossible, pseudo-science standard of "health".
A Better Option
Waist-to-hip ratio considers race and gender differences as well as accurately determines abdominal fat compared to gluteofemoral fat (fancy word for hip and butt fat). I've attached links here and here to measure and determine your WHR. It is a much more accurate predictor of obesity and mortality. Starting in your fifth decade, I would recommend getting a full body composition test with DXA annually.
Full disclosure: I am not on the "every body is a healthy body", body positivity bandwagon. Here is what I do fully endorse: the number on the scale does not determine how healthy you are. For most people, you know if you're healthy. It's in your consistent, daily practices. You can see it in your skin, hair and nails. You can feel it in your gut, in your brain, in your joints and bones. If you haven't drugged your body into silence, it is talking to you all the time. First, it comes as a calm request, then in symptoms, then finally in disease. It tells you what it needs, all you must do is trust and listen.
Disclaimer:
The content on this site is for informational and educational purposes only. It does not substitute professional medical advice from your healthcare professional.
Resources:
The History and Faults of the Body Mass Index and Where to Look Next: A Literature Review - PMC (nih.gov)
Abdominal obesity and the risk of all-cause, cardiovascular, and cancer mortality: sixteen years of follow-up in US women - PubMed (nih.gov)
Do Elite Athletes Live Longer? A Systematic Review of Mortality and Longevity in Elite Athletes - PMC (nih.gov)
Associations of Muscle Mass and Strength with All-Cause Mortality among US Older Adults - PubMed (nih.gov)
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