New Changes with Weight Assessment

New Changes with Weight Assessment

August 3, 2023

Joy Stepinski, MSN, RN-BC

Earlier this summer the American Medical Association (AMA) advised that body mass index (BMI), a value calculated from a person’s height and weight, should not be the sole factor in deciding if a patient has a healthy weight. The problem with relying heavily on BMI is that it neglects the direct measurement of body fat.

According to the AMA website, the report conclusions stated that “numerous comorbidities, lifestyle issues, gender, ethnicities, medically significant familial-determined mortality effectors, duration of time one spends in certain BMI categories and the expected accumulation of fat with aging are likely to significantly affect interpretation of BMI data, particularly in regard to morbidity and mortality rates” [1].

As with most health markers, BMI is just one puzzle piece. In fact, a 1990 text book sheds light on how the term “ideal weight” was coined in the first place. The insurance company, Metropolitan Life, desired to encourage their insured people to keep their weight below average. Guidelines were based on arbitrary data [2]. Despite this limitation, generally people who are above these ideal body weights tend to have increased mortality.

BMI has historically been viewed as an imperfect measurement of obesity. It does not measure body fat nor take into account muscle mass [3]. People do not share identical body fat percentages, and therefore the relationship between BMI and body fat is not linear. Body habitus vary with respect to fat distribution, bone structure, muscle mass, and gender.

The AMA recommendation does not negate the ramifications of obesity, which is linked with heart disease, stroke, diabetes, and cancer [4]. Yet the consideration of BMI alone can lead to bias in measuring obesity [3]. Instead, the AMA suggests using BMI together with other information, such as visceral fat, body adiposity index, body composition, relative fat mass, waist circumference, and genetic or metabolic factors [1].

References:

1. American Medical Association. (2023). AMA: Use of BMI alone is an imperfect clinical measure. https://www.ama-assn.org/delivering-care/public-health/ama-use-bmi-alone-imperfect-clinical-measure

2. Zinn, S. L. (1990). Body size and habitus. In H. K. Walker, W. D. Hall, & J. W. Hurst (Eds.) Clinical methods (3rd ed.) (pp. 646 – 649). Butterworths. https://www.ncbi.nlm.nih.gov/books/NBK243/

3. Rothman, K. J. (2008). BMI-related errors in the measurement of obesity. International Journal of Obesity, 32, S56 – S59. https://doi.org/10.1038/ijo.2008.87

4. Centers for Disease Control and Prevention. (2023). Obesity and overweight. https://www.cdc.gov/nchs/fastats/obesity-overweight.htm