Health and the body mass index: Is BMI accurate?
One of the most significant factors tying the concepts of weight and overall health is the body mass index (BMI). This measurement tool is pervasive, used everywhere from doctor's offices to personal training sessions, and it's similarly used to guide many scientific studies related to weight or health.
BMI is comprised of a weight-to-height ratio, which has been used as a metric of (inaccurate) health.
Unfortunately, this metric doesn't consider any other influences, such as bone density, body composition, muscle mass, body fat percentage, sex and racial differences, and other environmental and biological influences.
BMI doesn't take into account things like bone density, muscle mass, racial differences, etc.
And even if BMI could accurately predict an "ideal weight," it still misses out on the bigger picture regarding someone's health. BMI does not consider a person's body fat, fat distribution, or muscle mass. Two people with the same BMI could have very different body compositions.
Indeed, factors that are generally considered more pertinent to someone's overall health or risk of premature death are things like their blood pressure, blood sugar levels, cholesterol levels, and overall cardiovascular strength and emotional well-being, among others. Weight, often, has little overall influence on someone's overall risk factor for specific health conditions.
There is no such thing as a normal BMI for everybody.
Thinner bodies and overall health
As much as the media, diet and fitness culture, and much of the medical community may insinuate otherwise, a thinner body does not necessarily equate to a healthier body. Thinner-bodied people can still have significant health problems.
Equally notable, people in larger bodies may not have an increased risk of mortality or other issues, according to some research.
Some studies have concluded that as many as 50% of people who the medical community may consider "obese" according to BMI measurements were actually healthy and not experiencing the symptoms of a metabolic syndrome, such as high blood pressure, blood sugar, and abnormal cholesterol levels.2 These issues are often a more significant indicator of someone's overall health than their weight.
50% of those considered "obese" according to BMI are healthy.
Additional issues with BMI
Created in the 19th century by a Belgium mathematician named Lambert Adolphe Jacques Quetelet, BMI calculation was not initially intended to measure an "average" weight, as in what would be considered "normal" for a given person. Instead, it was formed as a quick and easy way to calculate the average weight of a general population, created to help the government determine how to allocate resources.10
It's unclear how the measurement came to the forefront of modern medicine and continued to be pervasive in so many medical recommendations and extending into the medical literature. The rise of health insurance companies and their influence on the modern healthcare landscape in the United States may have something to do with it, as general or stereotyped health measurements may be used as a guide for insurance company decisions more so than individualized health information.
Whatever the case, what remains clear is that BMI misses many key factors that help determine an individual's health or even medical recommendations for different ethnic groups or other subsets of the greater population.
BMI and race
A significant and notable pitfall of BMI is the average healthy weight of Black women compared to white women.
Several studies have found that, when measured against each other, Black women tend to be healthier at higher weights than white women and maintain higher health at larger waist circumferences.3,4
Further research has revealed that middle-aged and older Black women and men had lower visceral adipose tissue—the body fat around the organs responsible for many serious health risks—than their white and Hispanic counterparts, despite similar waist circumference measurements and BMI.5
Unfortunately, the "one size fits all" notion of BMI may lead to well-meaning but ultimately misguided medical recommendations. A more nuanced and individualized understanding of weight—can help ensure that patients are examined and treated with that information in mind rather than comparing them to a biased and inaccurate measurement or even studies that have used the same tool to make a conclusion.
Other ways to measure health
Bodyweight is far from the only predictor of someone's overall health and well-being. There are many other facets to gather information h, which can indicate health or point to some disease risk or other concerns, including:
- Blood sugar levels
- Blood pressure and resting heart rate which can be an indicator of heart health.
- Cholesterol levels,
- Number of hours slept, which is essential for cognitive and emotional health
- Amount of movement/exercise which promotes mental wellness, overall wellness, health, healthy bones and may reduce the risk of cardiovascular complications.
- Amount of vegetables and fruits consumed, which is essential for wellness.
- Number of alcoholic drinks consumed (excessive alcohol consumption can increase the risk of developing some health problems).
- Hydration, which is essential to our overall health.
- Inflammation levels
- Smoking status, as smoking causes many health complications, including cancer, chronic obstructive pulmonary disease (COPD), and heart disease.
Yet, just like BMI, none of these measurements accurately portray health on their own. Instead, they can be used together to create a comprehensive picture of wellness.
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Diet culture, body weight, and pressure to be thin
Diet culture comprises a set of beliefs, values, and norms that pit "health," as achieved through thinness, as the most essential pursuit in life. The concept insinuates that there is only one "ideal" weight for everyone, overlooking other factors that may indicate someone's overall health. As such, these beliefs follow that those who reach this ideal are healthier, morally superior, and more deserving of love and respect.
Further, diet culture puts the responsibility of achieving optimal health on the individual. This fails to acknowledge all the biopsychosocial factors and systemic issues that influence a person's physical and mental health, including culture, the media, disease, genetics, social status, oppression, and discrimination, among others.9
Diet culture is pervasive, and the widespread adoption of these beliefs, even among some health professionals, can result in the spreading of fatphobia, weight stigma, ableism, and significant discrimination against people living in higher-weight bodies. This, in turn, can bring on internalized fatphobia and weight stigma, shame, weight gain, and mental health conditions such as anxiety, depression, suicidal ideation, and eating disorders.6,7,8
Many different body weights, shapes, and sizes can support a healthy person.
At the end of the day, many different body weights, shapes, and sizes can support a healthy human. Weight has nothing to do with health, and it certainly has nothing to do with morality. But unfortunately, these views can make it difficult for many people to feel love for themselves or even to receive unbiased medical opinions.
Should you have a target weight?
This question is not a simple one to answer. Several factors can go into someone's "ideal" or target weight, and these are highly individualized, taking into account considerations such as someone's medical history, age, race, activity level, metabolic factors, and overall lifestyle.
It is usual for someone's weight to change as they age, adapting to different conditions their body is exposed to or going through. Additionally, body weight naturally fluctuates, even over the course of a given day. So zeroing in on one specific weight may create an unhealthy focus on a number that will naturally change based on completely normal factors.
Focusing on other aspects of health can allow the effects of normal, real-life events, like having a large meal to celebrate something or having a rough week and missing out on exercise routines. Speaking with a doctor, eating disorder, or Health At Every Size (HAES) informed dietician may be the best way to determine this range.
Regardless of the outcome, it's also essential to lead with self-compassion. No matter what the doctor's office may say your "ideal" weight is, remember that the number on the scale is only one small part of who you are and your health, and it has nothing to do with the content of your character, your potential, or your talents.
The Health At Every Size movement has many recommendations to help you generally take care of yourself while building a routine that keeps you active and happy, all while maintaining respect and appreciation for your body and yourself.
