BMI Basics
BMI is a commonly used term in healthcare and fitness. BMI stands for body mass index. It came into use in the mid-19th century to identify an abnormal weight and height proportion in people. It is calculated using one’s weight in kilograms divided by height in meters. Adolphe Quetelet was a mathematician that developed the BMI measurement. He came up with the measurement because he was searching for a way to study the height and weight of populations (Zierle-Ghosh, 2022).
Today BMI is often used as a screening method for being overweight or obese. When you go to a doctor’s appointment they usually record your height and weight to calculate your BMI. Healthcare professionals are educated to use BMI levels as an indication of health but the overall patient’s assessment and history must also be considered.
BMI is a useful tool because it is simple, does not cost much money, and is noninvasive. Whereas other tests are much more expensive, not easily accessible to a primary care office, and/or are difficult to standardize. The CDC says that healthcare practitioners need to consider many factors when testing BMI and it should not be the only measurement considered regarding health.
The BMI of adults who are 20 years old or greater is all assessed using the same scale. The Centers for Disease Control’s BMI assessment categories are as follows; A BMI below 18.5 is considered underweight. A BMI of 18.5 to 24.9 is considered normal. A BMI of 25 to 29.9 is considered overweight. A BMI of 30 or greater is considered obese.
BMI Considerations
Many people perceive BMI as being a test of body fat but it actually measures excess weight. Studies have shown that BMI levels are linked to future health risks but it is not the only factor to consider. The CDC considers BMI an appropriate measure for obesity screening and health risks related to obesity. Other factors such as age, sex, ethnicity, and muscle mass must be considered. For example, a bodybuilder will weigh more and their BMI may put them in the overweight or obese category, even though the bodybuilder’s extra weight is due to muscle mass and not excess fat. This is just one example of why a patient’s whole assessment and history need to be considered.
Research studies indicate that higher BMIs are linked with obesity-related health problems. BMI should be used as an initial screening for adults but it needs to be considered along with other factors such as fitness level, genetics, age, and fat distribution. BMI testing is not perfect and can be skewed. BMI is not supposed to be used as a diagnostic tool, it is just a screening tool. It does not measure body fat directly.
According to Dr. Robert Shmerling at Harvard Health Publishing, “In general, the higher your BMI, the higher the risk of developing a range of conditions linked with excess weight including diabetes, arthritis, liver disease, cancer, hypertension, high cholesterol, and sleep apnea”. He believes BMI can be useful but it is not a perfect measurement of health. It is good for identifying someone who is at risk for certain conditions based on weight but there are other factors that need to be considered (Shmerlin, 2020).
Key Takeaways
BMI is a useful tool to measure excess body weight but not excess fat. It should not be the only indicator of health because there are other factors that must be considered when assessing a patient’s health such as age, fitness level, genetics, and fat distribution. Results of the BMI screening could be skewed due to various factors. In general, people with higher BMIs are at greater risk of obesity related diseases.
Resources
Centers for Disease Control and Prevention. (2021, August 27). About adult BMI. Centers for Disease Control and Prevention. Retrieved March 1, 2022, from https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html
Body mass index: Considerations for Practitioners. Centers for Disease Control. (n.d.). Retrieved February 28, 2022, from https://www.cdc.gov/obesity/downloads/BMIforPactitioners.pdf
Shmerling, R. H. (2020, June 22). How useful is the body mass index (BMI)? Harvard Health. Retrieved February 28, 2022, from https://www.health.harvard.edu/blog/how-useful-is-the-body-mass-index-bmi-201603309339
Zierle-Ghosh A, Jan A. Physiology, Body Mass Index. [Updated 2021 Jul 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535456/
