Understanding the Fat-Free Mass Index (FFMI)

What is FFMI?

The Fat-Free Mass Index (FFMI) is a metric that measures the amount of lean mass (muscle, bones, organs, and water) relative to your height. Unlike BMI, which does not distinguish between muscle and fat, FFMI gives a more accurate picture of your muscularity, making it particularly useful for evaluating muscle mass and overall body composition.

How to Calculate FFMI

The formula for calculating FFMI is as follows:

FFMI=Fat-Free Mass (kg) / Height (m)2

To calculate your FFMI:

1. Determine your Fat-Free Mass (FFM): First, you need to calculate your FFM, which is your total body weight minus your fat mass. This can be measured using methods like bioelectrical impedance, skinfold calipers, or DEXA scans. You can get an estimate based on the image below

2. Measure your height in meters: Convert your height into meters if it's not already.

3. Plug the values into the FFMI formula: Use the above formula to calculate your FFMI.

Image estimate FFMI for men

Image estimate FFMI for women

Interpreting FFMI Scores

FFMI values can be interpreted as follows:

• Under 17: Below average muscle mass

• 17-19: Average muscle mass

• 20-22: Above average muscle mass

• 23-25: Muscular; typically seen in athletes

• 26+: Extremely muscular; likely enhanced by bodybuilding or other intense training, sometimes with the aid of supplements or anabolic substances

For natural athletes, (i.e. not on steroids), a FFMI score of around 25 is often considered the upper limit.

FFMI vs. BMI: Why FFMI is Better for Muscle Mass Assessment

Body Mass Index (BMI) has been widely used as a quick screening tool to categorize individuals based on body weight. However, it fails to differentiate between muscle and fat mass. This is where FFMI steps in. FFMI provides a more accurate representation of an individual's muscle mass by accounting for fat-free mass (muscle, bone, water, etc.) relative to height.

This distinction is important because two individuals with the same BMI can have drastically different body compositions - one could have more muscle mass, and the other could have more fat. Further, someone with high muscle mass might have a BMI that categorizes them as overweight or obese, despite having low body fat and being in excellent health. FFMI, on the other hand, takes muscle mass into account, providing a clearer picture of your fitness level. FFMI helps to make this differentiation, making it a more reliable indicator for those focused on building muscle and improving physical fitness.

Research on FFMI and Muscle Mass Targets

Maintaining an FFMI within a healthy range is not merely about aesthetics; it has practical health benefits. A higher muscle mass contributes to improved metabolism, greater strength and better overall physical function, all of which are essential for a healthier, longer life. The research around FFMI is summarised below:

1. Understanding Natural FFMI Limits

Several studies have explored the upper limits of FFMI in natural athletes (those who have not used performance-enhancing drugs like anabolic steroids). A frequently cited study by Kouri et al. (1995) examined the FFMI of bodybuilders and found that the average FFMI of steroid-free male bodybuilders was around 22, with an upper limit near 25. This study established that a FFMI around 25 is typically considered the natural ceiling for most individuals.

• Key Insight: If you're aiming for a high level of muscularity without the use of performance-enhancing drugs, an FFMI of 22-25 is a reasonable and realistic target as a male. For health reasons, women should aim to have a higher percentage of body fat in order to have normal hormone production. Therefore, their target should be an FFMI of 16-22. Achieving FFMI within these ranges would place you in the upper echelon of natural muscle development.

2. FFMI in the General Population

Research indicates that the average FFMI for men in the general population tends to be around 18-20, while for women, it’s typically lower with an FFMI around 15-18, reflecting differences in natural muscle mass and body composition between the sexes.

• Key Insight: For individuals who are not bodybuilders but want to improve their muscle mass for health and longevity, targeting an FFMI between 20-22 for men and slightly lower for women can be both attainable and beneficial.

3. FFMI and Athletic Performance

Athletes in various sports often have higher FFMI values due to their training regimes, which emphasize muscle growth and maintenance. For example, studies on collegiate athletes show that football players and wrestlers often have FFMI values in the 22-26 range. These athletes benefit from higher muscle mass not only for performance but also for enhanced metabolic health.

• Key Insight: For those aiming to optimize their athletic performance alongside health, an FFMI target of 22-26 may be ideal, especially if your sport demands significant strength and power.

4. FFMI and Longevity

Higher FFMI scores have been associated with lower mortality risk, particularly in older adults. A study published in The American Journal of Clinical Nutrition (2002) found that higher muscle mass was associated with better survival rates in elderly men, suggesting that maintaining a higher FFMI can contribute to longevity.

• Key Insight: Maintaining a healthy FFMI (20-25) as you age is crucial for reducing the risk of age-related muscle loss (sarcopenia) and for improving overall longevity.

Higher muscle mass is associated with a range of health benefits, including:

• Improved Metabolic Health: Muscle tissue helps regulate blood sugar levels and improves insulin sensitivity, reducing the risk of metabolic diseases like type 2 diabetes.

• Enhanced Physical Function: Stronger muscles support better mobility, balance, and overall physical function, reducing the risk of falls and injuries as you age.

• Increased Lifespan: Studies suggest that higher muscle mass is associated with a lower risk of mortality, making it a key component of longevity.

Thus, maintaining or improving your FFMI is crucial for longevity.

5. FFMI and Health Risks

It's also important to note that FFMI should be balanced with other health metrics. Extremely high FFMI values, especially those exceeding 26, might be associated with risks if achieved through unnatural means or if accompanied by excessive body fat. Therefore, while aiming for a higher FFMI is beneficial, it’s essential to ensure that it aligns with a healthy body fat percentage and overall lifestyle. Generally, a body fat percentage between 10-20% if felt to be a healthy range. [For more information about body fat targets, click here]

• Key Insight: Aim for an FFMI that is realistic and sustainable, without compromising other aspects of health. For most individuals focused on longevity, an FFMI in the range of 18-25, combined with a healthy body fat percentage, will yield the best long-term health outcomes.

Using FFMI to Set Fitness Goals for Longevity

Assessing your FFMI is particularly valuable when setting fitness goals focused on longevity. If your FFMI is below average, it might indicate a need to focus on strength training to increase muscle mass. Conversely, if your FFMI is already high, your goals might shift towards maintaining muscle mass while ensuring your body fat percentage remains in a healthy range. You can prioritise other fitness goals for longevity such as improving your flexibility and metabolic health with Zone 2 training. [Click here to find out more about Zone 2 training].

Summary of Target FFMI Ranges

• Average Adult (Men): 18-20

• Average Adult (Women): Slightly lower than men, approximately 15-18

• Athletic Individuals (Men): 22-26

• Athletic Individuals (Women): Approximately 19-22

• Natural Upper Limit (Men): Around 25

• Longevity Focus (Men): 18-25

• Longevity Focus (Women): 16-22

Practical Steps to Improve Your FFMI

If your goal is to increase your FFMI:

1. Prioritize Strength Training: Focus on compound movements like squats, deadlifts, and bench presses that work multiple muscle groups simultaneously. Aim for 3-4 strength training sessions per week.

2. Optimize Protein Intake: Ensure you're consuming adequate protein to support muscle repair and growth. A general guideline is 1.6-2.2 grams of protein per kilogram of body weight. [Click here for more information understanding your daily protein intake]

3. Balance Nutrition: While increasing muscle mass, it's important to maintain a balanced diet that supports overall health, including adequate intake of healthy fats, carbohydrates, and micronutrients. [Click here for more information understanding your daily macronutrient intake]

4. Adequate Rest and Recovery: Allow your muscles time to recover by getting sufficient sleep and taking rest days between intense workouts. Muscle growth happens during rest, not exercise.

5. Monitor Progress: Regularly track your muscle mass using tools like body fat scales, DEXA scans, or professional assessments to ensure your FFMI is improving over time.

Conclusion: Integrating FFMI into Your Fitness Goals

FFMI is a powerful tool for assessing muscle mass and setting focused fitness goals for longevity. By understanding and tracking your FFMI, you can tailor your fitness regimen to ensure you're building and maintaining the muscle mass necessary for a long, healthy life. Whether you're just starting your fitness journey or looking to optimize your current routine, incorporating FFMI into your assessment can provide the insight you need to achieve your longevity goals.