Has your doctor ever told you, you were overweight or obese? This is true in many cases, but for those who exercise frequently, it can paint an inaccurate picture of their health. Body mass index, or BMI, is “how much you weigh for your height and is used in the medical profession to screen for weight categories that may lead to health problems” (CDC, 2015).
BMI is calculated the following way
Table 1 BMI Classifications (Dwyer, Melanson, Sriprachy-anunt, Cross, & Wilson, 2000)
The issue with depending on BMI is that it only considers two metrics: weight and height. Well what about all of this:
For example, if you have a man with a BMI of 27, technically he is overweight. However, if his FFMI is 24.9 then that means 24.9 points out of the 27 is lean mass. We can then take into account his Waist circumference, let’s say 32 inches, well below the upper end of 40 inches for a male. And his waist to hip ratio is .76 inches. Way less than the .96 inches to require a concern. So yes, he is overweight, but with measurements like that, probably in excellent shape.
Simply relying on weight and body fat percentage will not give us all the answers to our overall health because, as we age, we tend to lose muscle mass. This is a phenomenon known as sarcopenia, which affects mortality. (Research findings on sarcopenia linked at the bottom of this article.) Also, body fat percentage “alone cannot explain the effects of ageing on FFM and the characteristics of subtypes of obesity” (Kim et al., n.d.). The two go hand in hand, as we age not only do we lose muscle mass but we tend to increase the amount of fat we have. If we rely on just BMI then we really do not have a clear picture as to what is going on.
Curious how you stack up? Use this online calculator to find out where you lie in the spectrum
References
ACE. (n.d.). Percent Body Fat Calculator: Skinfold Method. Retrieved from https://www.acefitness.org/education-and-resources/lifestyle/tools-calculators/percent-body-fat-calculator/
ACSM. (2014). Health-Related Physical Fitness Testing and Interpretation. In ACSM’s Guidelines for Exercise Testing and Prescritption (9th ed., p. 65). Wolters Kluwer.
CDC. (2015). Healthy Weight. Retrieved from https://www.cdc.gov/healthyweight/assessing/bmi/index.html
Dwyer, J. T., Melanson, K. J., Sriprachy-anunt, U., Cross, P., & Wilson, M. (2000). Dietary Treatment of Obesity. Endotext. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/25905223
Eberley, C. (2014). HYPERTROPHY EXPECTATIONS. Retrieved from http://exercisetoolkit.com/tag/fat-free-mass-index/
Gruber, A. / Pope, H. / Borowiecki, J. / Cohane, G. / I. S. for the A. of K. (2000). The development of the somatomorphic matrix: a bi-axial instrument for measuring body image in men and women. In Scientific conference; 6th, International Society for the Advancement of Kinanthropometry; 2000; Adelaide, Australia (p. 16). Sydney: Univ of NSW. Retrieved from https://www.tib.eu/en/search/id/BLCP%3ACN048374013/The-development-of-the-somatomorphic-matrix-a-bi/
Hui Wang, Shan Hai, Yixin Liu, Y. L. & B. D. (2019). Skeletal Muscle Mass as a Mortality Predictor among Nonagenarians and Centenarians: A Prospective Cohort Study. Scientific Reports, 9(2420), 1–7. Retrieved from https://www.nature.com/articles/s41598-019-38893-0#citeas
Kim, C.-H., Chung, S., Kim, H., Park, J.-H., Park, S.-H., Ji, J. W., … Kim, C. (n.d.). Norm references of fat-free mass index and fat mass index and subtypes of obesity based on the combined FFMI-%BF indices in the Korean adults aged 18-89 yr. Obesity Research & Clinical Practice, 5(3), e169-266. https://doi.org/10.1016/j.orcp.2011.01.004
Schuler, L. (2019). How Scientists Are Learning How to Use Your Muscles to Predict Your Mortality. Retrieved from https://www.menshealth.com/fitness/a27559880/muscle-cell-fiber-research-mentality/?fbclid=IwAR2uiYgqj_9xALFuN86NLLp1YI5GGNrHUdN1KDbEnJwecc1KljcjdS_5fuY