How Relative Fat Mass Index improves on Body Mass Index as a measure of health
Underweight. Normal weight. Overweight. Obese. These are the four categories the Body Mass Index (BMI) has used in its health assessment.
BMI calculation is based on two metrics: height and weight. Use one of many online BMI calculators and you will receive a number that is meant to indicate your general health. Below 18 and you are underweight. You are of normal weight if your BMI is between 18.5 and 25, overweight if it is between 25 and 30. Anybody with a BMI of 30 or more is obese.
However, more reports and studies are finding fault with BMI as a measure of health. Basing a calculation of health on height and weight alone, BMI doesn’t take into account bone, muscle, or fat proportions. This means that a person with exceptional muscle tone and low fat is more likely to have a higher BMI compared to someone with higher fat and lower muscle tone — because muscle can be four times as dense as fat.
If the BMI is defective, why are we still using it? Is there an easy alternative to the BMI? Yes, and it’s the relative fat mass index (RFM).
Studies have determined that your waist circumference provides a more accurate reading of your abdominal fat and risk for disease than BMI. Based on data from 3,456 patients in the United States, the RFM measurements closely matched those taken by a high-tech DXA body scan, widely considered the gold standard for measuring body tissue, bone, muscle and fat.
To get your new RFM measurement, measure your height and waist circumference, then plug the figures into this formula:
MEN: 64 – (20 x height/waist circumference) = RFM
WOMEN: 76 – (20 x height/waist circumference) = RFM
What’s interesting about the RFM is that weight is not even part of the overall equation. Additionally, there are no strict categories for simple classification.
As doctors and organizations like the American Society for Nutrition and the American Diabetes Association promote waist-circumference measurements as a supplement to, or replacement for, the body mass index, we are starting to rethink the relationship between weight and overall health. So, let’s say goodbye to the BMI and embrace the change that comes with new information that will hopefully lead us towards a more holistic view of wellness.