Researchers calculate body mass index (BMI) when collecting demographic data and publishing research. In public health messaging, BMI is used as a quick and easy screening tool to assess if you are of healthy weight (CDC, 2021).
BMI provides a crude measure of body fat. As body fat is correlated with unhealthy outcomes and various health risks, BMI measured repeatedly during coaching provides useful data to both the client and coach on the effectiveness of a weight-loss and exercise program.
If your goal is to lose weight, then you want your BMI to decrease.
If you goal is to gain weight, then it may be appropriate to track if your BMI increases.
The BMI Equation
BMI is a ratio of two biometrics: your height and weight
The equation = our weight (in kilograms) / your height (meters squared)
or…
BMI = Kg/m^2
Once calculated, you are left with a number often between 15-50. When you Google “BMI”, you will be provided with a countless images of the arbitrary cut points based on this ratio like this one:
The cut points and categories are as follows:
- Underweight = BMI < 18.5
- Normal Weight = 18.5 < BMI <24.9
- Overweight = 25 < BMI < 29.9
- Obese = 30 < BMI < 34.5
- Extremely Obese = BMI > 35
How to Use BMI?
While BMI is a crude measure to start with, there are many other behavioral targets and outcomes to focus on as well. Measures including step counts, calories consumed, total exercise time, and overall satisfaction with your current state of health and fitness.
Calculating BMI data are useful to capture every 3- to 6-months.
Reference:
Center for Disease Control (2021) About Adult BMI https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html
