BMI Is a Flawed Way To Gauge Fat and Obesity, Key Medical Association Says

New guidelines have been released by the American Medical Association (AMA) regarding the use of body mass index (BMI) because of the flaws of the metrics.

Body Mass Index

According to the Centers for Disease Control and Prevention, body mass index, or BMI, refers to one's weight in pounds or kilograms divided by the square of one's height in feet or meters. A high BMI typically indicates that one has high body fat.

NBC News adds that, for most people, having a BMI of 30 or higher indicates obesity, while having a score of 25 to below 30 indicates that one is overweight.

This metric is typically used for screening weight types that may lead to health issues. However, it does not diagnose a person's body fat or overall health.

BMI as an Imperfect Metric

While the BMI has been a widely used metric, it has been seen as a flawed body fat measure with a history full of issues. Live Science adds that the measure should be used alongside other health risk metrics, such as blood pressure, genetics, cholesterol, and other metabolic considerations. These were laid out in the AMA's new guidelines.

A new report was relayed during the 2023 AMA's Annual Meeting in Chicago just this month. During the presentation, council members indicated that BMI does not differentiate between a person's lean body mass and body fat. Other than that, BMI also does not shed light on the specific body regions where excess fat can be found.

Live Science explains that such considerations are important due to how fat in the upper body boosts the chances of developing coronary artery disease and type 2 diabetes compared to lower body fat.

The AMA explained in a statement that despite how easy and cheap it is to use and calculate BMI, the metric is inaccurate in gauging body fat across several groups. This is because the metric does not consider the various bodily differences in terms of body shape and demographics, such as ages, races, sexes, and ethnicities.

The statement adds that this is mainly due to how the scale is based on data obtained from earlier generations of non-Hispanic white populations. The AMA explains that the cutoffs of the BMI are grounded in the idealized Caucasian.

This means that such thresholds do not show the same risk extent for every patient. Live Science notes that overall the use of BMI in medical research leads to a skewed understanding of the disease and death risks associated with obesity.

The report also adds that for studies that demonstrate a link between high BMI and death or disease, other factors failed to be taken into account. These factors may include one's alcohol use, smoking, history of disease in the family, and medications. Such studies also do not typically consider the typical weight fluctuations that accompany age and lack understanding regarding the time participants spend in a particular category of the BMI.

Hence, the AMA has implemented new policies regarding the use of the BMI. Due to the metric's limitations, it should be used alongside other valid methods of gauging risk. The association also stressed that leaning too much on the BMI may lead to undertreatment and underdiagnosis of conditions.

Dr. Jack Resneck, Jr., the AMA's immediate past president, explains how important it is for physicians to know the limitations and benefits of utilizing BMI in clinical contexts in order to identify the best care that can be offered to patients.

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