“A study on Division 1 and Division 2 college football players found that the average Fat-Free Mass Index for offensive linemen was 25.1, indicating that an FFMI above 25 is naturally achievable for some athletes without the use of anabolic steroids.”

An important finding of the current study was that 23 athletes (21%) had a FFMI above 25 kg · m−2 (range: 18.1 – 27.7 kg · m−2). This study demonstrates that an athlete’s upper limit for FFMI may extend well beyond 25 kg · m−2, and differences exist across positions for collegiate American football.

The current study evaluated upper limits for FFMI in collegiate American football players (n=235). Sixty-two participants (26.4%) had FFMI~Adj~ values above 25 kg·m−2, including 31.3% of Division I participants. The current findings demonstrate that collegiate American football players may realistically strive for FFMI values well beyond 25 kg·m−2.

The current study evaluated upper limits for FFMI in collegiate American football players (n = 235)... Differences were observed among position groups (p < 0.001; η = 0.25), with highest values observed in offensive linemen (OL) and defensive linemen (DL)... Sixty-two participants (26.4%) had height-adjusted FFMI values above 25 kg·m (mean = 23.7 ± 2.1 kg·m; 97.5th percentile = 28.1 kg·m). Upper limit estimations for FFMI seem to vary by position.

The normalized FFMI values of athletes who had not used steroids extended up to a well-defined limit of 25.0. Similarly, a sample of 20 Mr. America winners from the presteroid era (1939-1959), for whom we estimated the normalized FFMI, had a mean FFMI of 25.4. By contrast, the FFMI of many of the steroid users in our sample easily exceeded 25.0, and that of some even exceeded 30.

The overall mean FFMI was 23.50 ± 2.04 kg· m−2... FFMI was highest in linemen (24.8 ± 1.5 kg· m−2)... Our findings suggest that the upper limits for FFM accretion in male athletes may be higher than previously assumed, as the FFMI limit of 25 kg· m−2 underestimates that observed in American collegiate football players... current findings highlight that collegiate American football players have the potential to achieve FFMI values significantly exceeding 25 kg· m−2.

In an examination of 157 athletes, comprising 83 steroid users and 74 nonusers, we calculated normalized FFMI using height, weight, and body fat based on skinfold measurements. With this simple measurement, we found that athletes who had not used steroids all had values of <25.0, whereas a large proportion of steroid-using athletes easily exceeded this limit. It appears that FFMI may represent a useful initial measure to screen for possible steroid abuse.

According to earlier research FFMI is a height-adjusted assessment of fat-free mass (FFM), which is derived by dividing FFM (in kilograms) by height (in square meters). Further research suggested a natural upper limit of 25 kg·m2 in resistance trained male athletes. [The study evaluated collegiate football players and found evidence contradicting this limit.]

The overall mean FFMI was 23.50 ± 2.04 kg · m−2, with values ranging from 18.1–27.7 kg · m−2. FFMI was highest in linemen (24.8 ± 1.5 kg · m−2)...

The foundational FFMI study analyzed 157 male athletes and established that the natural upper limit for drug-free muscle development centers around an FFMI of 25. However, updated research (2000-2025) suggests that rare genetic outliers (top 0.1-0.5% of population) are capable of reaching FFMI 25-26 naturally with elite training and nutrition.

This study proposed that the natural FFMI limit in American collegiate football players is higher than 25 kg.m2 irrespective of which height adjustment equation was used. Mean FFMI greatly varied between different position groups... Division I players FFMI were observed to be higher than to Division II players.

Some documented natural athletes have achieved FFMI scores slightly above 25; Genetic variations in muscle fiber distribution and hormonal profiles. Current scientific consensus: While FFMI > 25 strongly suggests enhancement, achieving 24-25 naturally is possible but requires exceptional genetics.

Natural muscle potential exists on a bell curve, and genetic outliers can and do naturally exceed an FFMI of 25. This has been confirmed in other studies on drug-free athletes. The idea of a hard 'natural limit' at a 25 Fat-Free Mass Index (FFMI) stems from a misinterpretation of a single 1995 study.

Offensive linemen in both college and professional offensive football had the lowest LULLR. The low LULLR coupled with the high TULLR... suggests that the offensive linemen have a higher percentage of fat mass in their trunk and arms compared to the muscle mass of their legs.

For offensive linemen, the mean weight increased nearly 38 percent, while the control group experienced only a 12 percent increase.

For years, many believed that a natural (drug-free) lifter couldn't exceed an FFMI of 25. This idea came from a 1995 study that found none of their 74 drug-free gym-goers exceeded 25, while nearly half of steroid users did. In the years since this paper was published, people have started using the FFMI cutoff of 25 as an unofficial 'screening test' to identify steroid users.

Fat-free mass index (FFMI; kg/m2) is a height-adjusted assessment of FFM, which helps normalize values and improve generalizability for recommendations across sports. For strength and power athletes, upper limits of FFMI can be used to evaluate potential for FFM gain.

None of those natural lifters had FFMIs of over 25, but about half of the steroid users did. This suggests that most natural lifters don’t have an FFMI of over 25, but it says relatively little about what’s physically possible, especially when looking at outliers. The myth of the natty limit comes from an old Kouri study from 1995.

The seminal 1995 study by Kouri et al. analyzed 157 male athletes: 74 natural with normalized FFMI up to 25.0, and 83 steroid users often exceeding 25. The study proposed FFMI >25 as a strong indicator of steroid use, though it noted this as a statistical threshold, not an absolute limit, and called for further research on outliers.

Most female college athletes in strength-related sports had FFMI values around 20-22, but values up to (and beyond) 27 are possible. Of the 372 athletes, the 97.5th percentile was 23.9. However, values as high as 27.2 were observed! These results are fairly consistent with another recent paper by Blue et al (2019), which documented several female athletes in the low-20s, and maximal observed values above 25.

The researchers have conducted a study with 157 athletes – those who admittedly were steroid users (n=83) and those who weren’t (n=74) and calculated their FFMIs. They found that the average FFMI among users was 24.8±2.2 and among non-users – 21.8±1.8. The recommended cut-off score is 25 i.e. if someone’s FFMI is 25 or higher it’s very likely that they are steroid users (according to the authors).

Based on one single study in 1995, researchers gathered 157 people, 74 of whom were natural and the rest were drug-using athletes or have been using drugs in the past. The researchers reported that the highest FFMI found in the natural group was less than 25, whereas a large proportion of steroid-using athletes exceeded this limit.