Body Mass Index (BMI) is a ratio of one’s body weight to height, and is often used as a marker for increased health risks.[1,2] Generally speaking, a high BMI is an indication of high body fat mass. A BMI value between 19-24 is considered within the “healthy” range, with any value below considered underweight and any value above considered overweight. BMI values above 30 are considered obese, and above 40 morbidly obese. You can easily find your BMI on the chart below.
Is BMI a good measurement tool to assess relative health status? In recent years it has been challenged by the medical community as lacking in its ability to account for a variety of variable factors. In what ways do BMI measurements fall short?
It wasn’t designed to estimate the health risk of a single individual.
The BMI formula was created by mathematician Lambert Adolphe Jacques Quetelet, who designed it as a shortcut to estimate the general health risk of an entire population to aid in the allocation of government resources. Not to mention, is was introduced in the early 19th century—outdated to say the least.
It doesn’t take into account waist circumference.
Waist circumference is an established indicator of potential health risks.[3,4] BMI, which evaluates a person’s weight relative to their height, does not utilize this measurement to help establish prevalence of health risks—falling short in its ability to predict such risks.
It doesn’t account for muscle mass.
BMI utilizes bodyweight to generate a value, but doesn’t have any process for specifying the body composition of the individual. As an example, an individual with extra muscle mass may fall within the obese range on the BMI scale simply because the extra muscle adds additional weight. Carrying an extra fifteen pounds of muscle is much different than carrying an extra fifteen pounds of body fat.
It is an oversimplification of health status.
Another method of measuring overall health, referred to as “cardiometabolic health,” involves taking measurements such as blood pressure, cholesterol levels, and blood sugar to measure a person’s risk for developing heart disease or diabetes. Studies have shown that there are many people who fall within the normal BMI range, yet show signs of increased health risk due to their cardiometabolic measurements, and vice versa individuals marked as overweight or obese who have otherwise normal bloodwork.[5]
Weight and BMI measurements alone do not provide a comprehensive picture of the potential health-status of an individual. Body composition measurements, in addition to cardiometabolic measurements, should be used to evaluate the potential risk factors of an individual.
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That darn BMI. It’s confused me for years. Thanks for the post, I feel like I’m understanding it a little better now!