Is BMI an Accurate Measure of Health?

The body mass index (BMI) is an anthropometric calculation that divides mass by height squared. In modern practice, this number is used to assess a person's health. For example, if their mass relative to their frame is within a healthy range. Over the years, several arguments have highlighted why this superficial tool is not a reliable indicator of health. Keep reading to learn what to use instead and why.

Key takeaways:

What is BMI?

The initial version of the body mass index (BMI) formula was created by Dr. Quetlet in the 1800s and was used to quickly assess the average size of a person and how it compares to others. He adored combining statistics with health and was the first person to assign “health averages” for the population. This data could be used to predict health trends and disease risks.

Much later, in the 1970s, the BMI formula (BMI=kg/m2) was used to index obesity at an individual level. The World Health Organization (WHO) embraced this method in the 90s, and the BMI formula suddenly became engrained in individual patient care. A person's score indicated if they were underweight, normal weight, overweight, or obese.

The current BMI categories are:

BMI ScoreBMI Classification
<16kg/m2Severely underweight
<18.5 kg/m2Underweight
18.5–24.9 kg/m2Normal weight
25.0–29.9 kg/m2Overweight
30.0–34.9 kg/m2Moderately obese
35–39.9 kg/m2Severely obese
>40.0 kg/m2Morbidly obese

Why isn't BMI a good health measure?

A significant flaw of the BMI equation is that it does not differentiate between healthy mass, muscle tissue, and body fat.

If relying solely on BMI as a metric for health, people may rank higher and be classified as obese despite being perfectly healthy. For example, athletes may have a heavier mass than the average person and may rank as obese (even though visually, we can see they are not.) Pregnant women may also be classified as overweight or obese even though it is clear the sudden increase in mass is coming from the growing baby.

Being healthy but constantly told otherwise because of one's body size can harm long-term health. People who experience weight stigma are less likely to seek medical care because of the unwanted focus on their weight. This includes avoiding appointments for non-weight topics, such as eye infections or earaches.

There is also a risk that someone living with a more petite body is assumed to be healthy when they may have genetics that naturally predisposes them to certain chronic illnesses. This is seen in different cultures worldwide, and 2021 research highlighted the prevalence of type two diabetes in South Asian and Chinese populations despite being within the healthy BMI range.

Then why is BMI still being used?

Unfortunately, the BMI is still used in clinics because of its simplicity — it is one of the quickest anthropometric calculations a healthcare provider completes. Moving forwards, all aspects, traits, and characteristics must be considered to improve patient care. How is their mood? What is their energy level? How is their metabolic health?

Yes, there is a link between weight and disease. The CDC states that people who are overweight or obese are at an increased risk of colon diseases and cancer, gallbladder disease, liver disease, and hormone dysfunction.

However, calculating BMI is insufficient to assess a person's health and understand their disease risk. Further testing is the only way to understand a person's health status. This includes stress tests, blood work, blood pressure checks, and physicals.

What's a better measure of health?

Completing bloodwork to assess metabolic health is essential for assessing overall health. A physician should assess cholesterol levels, blood sugars, liver function, and other relevant metabolic markers.

It is wise to check blood pressure regularly because high blood pressure (called hypertension) is a silent condition. Over-the-counter devices can be purchased at most pharmacies to check pressure at home. The target ranges may vary slightly based on medical history, but a healthy blood pressure range generally is 120/80.

Additionally, a tape measure can be used to assess waist circumference. Fat stored around the midsection is more hormonally active. As a result, carrying more weight in this area increases disease risk. This measurement is more specific than a BMI calculation because it focuses on visceral tissues.

How can we improve our health?

We can improve our healthy by exercising more. No single food, supplement, or medication can improve our health as significantly as regular physical activity. To increase overall movement, something as simple as a short walk before bed does wonders. Getting an exercise buddy helps us stay committed and motivated.

Working with a dietitian also helps us make proper dietary changes to support long-term health. For instance, 2023 nutrition research highlights that following a plant-based diet is more beneficial for reducing the risk of disease.

These small changes are non-weight-focused, and improvements in these areas of life support better health even if our weight remains unchanged.

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