The differences between using BMI and FFMI to determine your muscle mass
BMI History, Formula, and Limitations
History
Adolphe Quetelet, one of the 19th century’s most influential statisticians, sought to define a normal man. Using data from several hundred of his Belgian compatriots, Quetelet noticed that his countrymen’s weight varied in proportion to the square of height, rather than weight being in direct proportion to height as had been previously assumed. This meant that the previous assumption that people 10% taller than average were 10% heavier was replaced with the assumption that people 10 percent taller than average tended to be about 21 percent heavier. He released these results in 1832! In 1972, Ancel Keys coined the term Body Mass Index for Quetelet’s formula.
Formula
The metric formula for BMI is weight in kilograms (kg) divided by height in meters squared (m²). [weight (kg) / height (m²)]
The imperial formula for BMI is weight in pounds (lbs) divided by inches squared (in²). The total is then multiplied by 703. [(weight (lbs) / height (in²)) x 703]
Limitations
BMI doesn’t take into account differentials like gender, age, muscle mass, bone density etc. Note that for somebody who exercises daily or trains professionally, BMI is mostly useless when it comes to determining your ability to function or perform well in everyday life or physical activities.
FFMI History, Formula, and Limitations
History
The concept of Fat-Free Mass Index (FFMI) has been used in exercise science and body composition analysis for several decades, but there is no specific date associated with its development. FFMI is essentially a variation of Body Mass Index (BMI), adapted to assess an individual’s muscle mass relative to height.
The calculation and use of FFMI have evolved over time as our understanding of body composition and fitness assessment has advanced. Researchers and fitness professionals have been using similar formulas and concepts to assess lean body mass and muscle-to-fat ratios for many years.
While there may not be a precise date of origin for FFMI, it has become more widely recognized and used in the context of bodybuilding and fitness communities as a way to assess muscle development and body composition. It’s important to note that FFMI is just one of several methods for evaluating body composition and should be considered alongside other relevant factors when assessing an individual’s fitness and health.
Formula
FFMI = Lean Body Mass (kg) / (Height (m²)
If fat mass increases, FFMI goes down, and if muscle mass increases, FFMI rises allowing you to estimate someone’s body and health condition correctly.
Limitations
It’s not a perfect index, in that it doesn’t tell you how “healthy” you are. But it does provide you with a good idea of whether you have the muscle mass to support your lifestyle and performance aspirations.