What is FFMI and what does it show?

First of all we should start by mentioning that this is an index used to account for the amount of muscle mass one person carries in correlation to their weight and height. It belongs to the class of body weight indexes along with the BMI but it takes things to a different level and becomes much more specific.


It also addresses one of the criticisms of BMI: two people with different weights and heights may have the same BMI but different amounts of fat / muscle. BMI can classify a person with a lot of muscle mass into a higher class, perhaps an indication of negative health, regardless of body type, because it does not consider the difference in tissues and uses only the total weight.

In trying to address these problems, studies have been made, as cited in the references section, on steroid and non steroid users, bodybuilders in contest shape, to determine an index and its range, something that could adapt to specific body masses.


Besides the formula of FFMI and adjusted FFMI it was concluded that a normal average index score for males is around 19 while everything going above 25 is indicative of steroid usage.

This also marked the beginning of a gold criterion screening standard for steroid use in bodybuilders. However, this doesn’t necessarily mean that a person cannot attain naturally a score of 30 but it is highly unlikely.

Basically this index helps track fat loss progress as well as muscle building processes you might be going through and is often used by athletes, fitness enthusiasts or body builders.


FFMI interpretation and norms for men


As discussed above, the proposed studies have reached the following conclusions in regard to what the scores mean about the body condition of the subjects. These scores are now used in practice and provide useful guidelines to everyone who wants to know where they stand in terms of muscle mass:

■ 16 – 17: below average

■ 18 – 19: average

■ 20 - 21: above average

■ 22: excellent

■ 23 – 25: superior

■ 26 – 27: scores considered suspicious but still attainable naturally

■ 28 – 30: highly unlikely scores to be obtained naturally without steroid usage



Example calculation of fat free mass index





Let’s take for example a fitness enthusiast with a weight of 180 lbs, 12% body fat and 5 ft 10 in height. The result from the above form will be

- Lean mass = 71.85 kg / 158.40 lbs

- FFMI = 22.78

- Adjusted FFMI = 22.91

When trying to make all sorts of calculations and you want to discover how much muscle mass you can build at your stature you can try different numbers in the weight and body fat fields and see which combination will take you to a value close to 25, which is considered an obtainable FFMI score without any chemical intervention.

Therefore this calculation can provide useful information about the muscle mass.




References
1) Schutz Y, Kyle UU, Pichard C. (2002) Fat-free mass index and fat mass index percentiles in Caucasians aged 18-98 y. Int J Obes Relat Metab Disord; 26(7):953-60

2) Kouri EM, Pope HG Jr, Katz DL, Oliva P. (1995) Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med; 5(4):223-8.