Average Lean Body Mass (And How to Optimize It)

The average Lean Body Mass (LBM) varies by sex and age — 60-80% in men and 50-70% in women. More than 75% LBM in men & 68% in women may indicate health concerns.

To build a fit and healthy physique, you’ve got to understand your body composition. Standing on a scale will tell you how much you weigh but won’t shed light on how much muscle and fat you carry. For that, you need to know your lean body mass.

Whether you’re an athlete focused on performance enhancement, a lifter wanting to pack on some muscle, or a senior trying to negotiate the changes that come with aging, a comprehensive understanding of lean body mass is needed to make informed decisions about nutrition, exercise, and well-being.

In this article, we’ll break down everything you need to know about lean body mass, including what it is, how to calculate it, the factors that influence LBM, and how you can increase your lean body mass percentage. We’ll also reveal the average lean body mass so you can see how you compare to the rest of the population. 

Average Lean Body Mass For Men and Women

The American Council on Exercise regularly publishes body fat percentage statistics. By subtracting these percentages from 100, we can determine Americans’ average lean body mass. The following statistics are sourced from ACE. (1)

Average Lean Body Mass Percentage by Age for Men:

Age Category	Average LBM
18-24	75.19
25-29	74.6
30-34	72.24
35-39	71.47
40-44	71.66
45-49	71.83
50-54	70.75
55-59	70.67
60-64	69.83
65-69	68.94
70-74	68.90
75-79	68.47
80+	68.90

Average Lean Body Mass Percentage by Age for Men:

Age Category	Average LBM
18-24	62.2
25-29	61.52
30-34	59.73
35-39	59.01
40-44	57.62
45-49	59.87
50-54	57.59
55-59	56.73
60-64	56.0
65-69	55.09
70-74	55.4
75-79	56.05
80+	55.86

These figures do not paint a pretty picture. It shows that the average American is carrying too much body fat and far too little muscle mass. We clearly see this when we compare the above statistics to the lean body mass standards.

The following chart shows healthy lean body percentage ranges by age:

Age	Healthy LBM Women	Healthy LBM Men
20-39	68-79%	81-92%
40-59	67-77%	79-89%
50-69	65-76%	76-87%

Understanding Lean Body Mass

Your lean body mass (LBM) is a measure of your fat-free weight. It includes the following:

• Muscle
• Bones
• Blood
• Skin
• Internal organs
• Ligaments
• Tendons

Your LBM will include a small amount of essential fat contained within the bone marrow and your internal organs. Essentially, though, it is how much you weigh when your body fat percentage is taken out of the equation.

How to Calculate Your LBM

The most precise way to calculate your lean body mass is with a DEXA scan. This involves the use of low-dose X-rays to measure bone density, lean muscle mass, and fat mass. However, this method may not be readily accessible and is quite expensive. You will have to make an appointment at a clinic that offers the service, with the cost being between $100 and $300. 

Fortunately, there is a much more accessible and cheaper way to work out your LBM. Here’s a four-step method that will give you a relatively accurate result. You will need a body fat scale for the first step. These scales are relatively inexpensive and usually quite accurate:

Step One: Check your weight and body fat percentage on a body fat scale. 

Let’s say you weigh 200 pounds, and your body fat percentage is 20 percent.

Step Two: Subtract your body fat percentage from 100. This gives you your lean body mass percentage.

In the above case, your lean body mass percentage would be 80 percent.

Step Three: Divide your LBM percentage by 100.

This gives a result of .80 in the above example. 

Step Four: Multiply your Step Three result by your body weight. This will tell your lean body mass.

So, a 200-pound person with 20 percent body fat will have an LBM of 160 pounds. 

Here’s an example of a female carrying 30 percent body fat at a body weight of 150 pounds.

• Step One: 150 pounds / 30 percent body fat
• Step Two: 100-30 = 70 percent lean body mass
• Step Three: 70 /100 = 0.7
• Step Four: 150 / 0.5 = 105 pounds of lean body mass. 

So, the 150-pound woman has an LBM of 104 pounds. That means that she is carrying 45 pounds of body fat. If she lost half of that body fat, her physique and general health would improve dramatically. So, a good goal for her would be to lose 22 pounds. 

If you want to avoid the math, you can use our lean body mass calculator to work out your LBM.

Why You Must Know Your LBM

Our objective in altering body composition is to boost lean muscle while reducing body fat. Without knowing these metrics, you’re merely speculating about your progress.

In my experience as a personal trainer, most people are obsessed with weight loss. Their one and only goal is to drop pounds on the scale. TV shows like The Biggest Loser perpetuate the idea that dropping weight is all that matters. 

But the scale (unless it’s a body fat scale) won’t tell you whether you’re losing fat or losing muscle, bone tissue, or something else. 

Since muscle tissue is denser than body fat, you might lose significant fat and gain a bit of muscle without any change on the scale. Or, if you gain a little bit more muscle, you may actually see an increase on the scale. 

From what I’ve seen, people often panic when they notice an increase on the scale after a month of consistent exercise. Only when they are educated about the difference between body fat percentage and lean body mass do they come to appreciate that their body composition is changing for the good. 

The bottom line here is that unless you are monitoring your lean body mass, you are essentially operating in the dark. But by regularly monitoring your LBM percentage, you can see what’s happening in terms of the amount of muscle and fat you have in your body. 

Factors Affecting Lean Body Mass

Increasing your lean body mass is something that is largely, but not totally, within your control. Here are some factors that affect your LBM:

Gender

Women have an average higher body fat percentage than men. As a result, the average LBM for females is lower than that for males. This is due to biological and hormonal factors.

Women require more body fat for reproductive purposes. A certain amount of body fat is needed for healthy menstrual activity and fertility. Women who have body fat percentages below around 12 percent will experience interruptions to their monthly menstrual cycle. 

Higher levels of fat storage also benefit pregnancy and lactation. These stores of reserve energy allowed women to feed their babies during times of food scarcity. 

Men have an average higher basal metabolic rate (BMR) than women. As a result, they burn more calories at rest than women. This contributes to a higher body fat percentage and a lower LBM in females.

Men also tend to have more muscle mass than women. Muscle is more metabolically active than fat, contributing to men’s more efficient fat-burning capacity.

Estrogen is the primary female sex hormone. It contributes to fat storage in women, especially in the hips, breasts, and thighs.

Genetics

Genetics helps determine a person’s ability to build lean muscle and store body fat. Your distribution of type I and type II muscle fibers is genetically predetermined. This ratio influences your endurance, strength potential, and ability to build muscle mass.

Muscle structure and density are also affected by genetics. Your ability to build large, dense muscle tissue is a product of hard work, smart nutrition, and genetic predisposition. 

There is a genetic component to your metabolic rate. A person with a fast metabolism may find it easier to lose fat but more challenging to gain muscle. Your levels of the primary anabolic hormones, testosterone and growth hormone, are also influenced by genetic factors. These affect your rate of muscle protein synthesis, directly affecting your muscle-building ability. 

Finally, bone density also has a genetic component. The amount of bone tissue you have directly affects your lean body mass. 

Age

A person’s lean body mass peaks in their late twenties and then gradually declines. This is largely due to age-related muscle loss, known as sarcopenia. From about the age of 30, we naturally lose 3-8 percent of our muscle mass every decade.  As a result, our lean body mass goes down. 

Sarcopenia results from several factors, including:

• A reduction in the rate of testosterone and growth hormone secretion.
• Reduced rate of muscle protein synthesis.
• A lack of exercise, particularly resistance training. 
• Insufficient protein intake.
• Age-related chronic inflammation. 

Physical Activity

Physically active people will have more muscle tissue and less stored fat. The more exercise you do, the more stored energy in the form of calories you will burn off. At the same time, you will be making your muscles bigger and stronger. 

You should concentrate on cardiovascular exercises that burn off calories to reduce body fat. Some of the most efficient fat-burning forms of cardio are:

• Rowing Machine
• Ski-erg
• Incline Treadmill 
• Swimming

To build muscle mass, you should perform resistance training with free weights and cable machines. Train each body part twice weekly with resistance levels that challenge you in the 8-12 rep range. 

Ensure that your muscles can recover fully between workouts. Allow a minimum of 48 hours of rest before training a muscle group again. Make sure, too, that you are getting 7-8 hours of sleep each night, as it is while you are sleeping that most of the muscle recovery and regrowth takes place. 

Nutrition

Nutrition plays a vital role in determining a person’s lean body mass. People who consistently consume more calories than their body requires to meet its energy needs will keep piling body fat onto their frame. This will increase their body fat percentage and decrease their amount of lean body mass.

Increasing lean body mass depends on developing and maintaining an anabolic nutritional environment. This includes consuming plenty of quality protein. Protein is made up of amino acids, which are the building blocks of muscle tissue. You should focus on proteins containing the nine essential amino acids the body cannot manufacture naturally.

Good animal sources of complete proteins are meat, fish, poultry, and dairy. The best plant-based sources are quinoa, soy, chia seeds, and buckwheat. 

How to Increase Your Lean Body Mass

Increasing your lean body mass requires the consistent application of four principles:

1. Eating for Muscle Gain and Fat Loss

Knowing how to eat for muscle gain can get quite complicated, so here are four simple rules to follow to create the ideal anabolic environment for muscle growth:

• Eat protein within an hour of your workout: This will provide the amino acids to facilitate muscle protein synthesis. This process happens as a response to the stress you put on the muscles during your workout. The muscle will recover and become slightly bigger and stronger to handle the same stress in the future.
• Combine carbs with your post-workout protein meal: Your workout will deplete your muscles of glycogen, which is processed carbohydrates. Besides replenishing muscle glycogen levels, carbs increase protein synthesis. Your post-workout meal should include 40-60 grams of fast-acting carbs.
• Stay hydrated: Many people are in a state of mild dehydration without even knowing it. When you do not have enough water, problems occur. One direct impact on muscle-building capacity is the reduced release of testosterone. Aim to drink half a gallon of water (2 liters) daily.
• Increase caloric consumption: To build muscle, you need to take in more calories than your body needs to meet its daily energy requirements. Go here to determine your daily calorie requirement, and then add 500 calories to it. 

2. Training All Muscle Fibers

To fully develop a muscle, you must work both the type I and type II muscle fibers. We mentioned earlier that your genetics determines the ratio of these fibers. Given that you can’t control that ratio, you do yourself a disservice if you neglect one of the them.

You should train with a wide rep range to work all of your muscle fibers. Working at a high rep range will primarily work your slow twitch muscle fibers, while lower reps will target your fast twitch fibers.

Here is a recommended rep system that will allow you to hit all muscle fibers:

• Set One: 30 reps
• Set Two: 20 reps
• Set Three: 15 reps
• Set Four: 10 reps
• Set Five: 8 reps
• Set Six: 6 reps

On each of these sets, you should add resistance so that you can barely complete the required rep count. 

3. Performing Cardiovascular Exercise to Reduce Body Fat

Cardiovascular exercise will improve the efficiency of your heart and lungs while also burning off stored body fat. I recommend performing 30-40 minutes of cardiovascular exercise 3-4 times per week. 

To give you an idea of what you could do, here is an overview of my current cardio schedule. 

Right now, a very popular form of cardio is the 12-3-30 treadmill workout that influencer Lauren Giraldo popularized. I’ve been personally doing this workout a couple of times per week and fully endorse it. It involves:

1. Set the incline on a treadmill to 12 percent.
2. Crank up the speed to 3mph.
3. Walk for thirty minutes.

I’m able to burn 250-275 calories on this workout. Two other times throughout the week, I train on a Ski-Erg. If you’re unfamiliar with this machine, it is basically an upright rowing machine that involves pulling with your arms rather than rowing with your legs. I follow a pyramid program based on calories burned as follows:

• 10 calories burned, rest 10 seconds
• 20 calories burned, rest 10 seconds
• 30 calories burned, rest 10 seconds
• 40 calories burned, rest 10 seconds
• 50 calories burned, rest 10 seconds
• 40 calories burned, rest 10 seconds
• 30 calories burned, rest 10 seconds
• 20 calories burned, rest 10 seconds
• 10 calories burned, rest 10 seconds

That works out to 250 calories burned in total.

At 7 a.m. every Sunday, I join some friends for a pretty steep mountain hike that takes about an hour.

4. Sleep

When people exercise, most of their focus is directed towards the one hour dedicated to physical activity. However, the outcome of their efforts is significantly influenced by the remaining 23 hours of the day, with particular emphasis on the hours spent in bed.

Insufficient sleep negatively impacts workout performance, diminishing the effectiveness of motor neurons and impairing execution abilities. Sleep-deprived exercisers tend to be less agile, slower, and have compromised reaction time. Conversely, those who enjoy a full eight hours of uninterrupted sleep tend to exhibit enhanced sharpness, agility, and motivation.

A 2007 study revealed that just a week of sleep deprivation can inhibit glucose uptake. This limitation in accessing glucose, the body’s primary energy source, can significantly impact workout performance. (2)

Here are six sleep-enhancing strategies to optimize lean body mass:

1. Establish a consistent sleep routine, ensuring a regular bedtime and wake-up time.
2. Invest in high-quality sleep equipment, including an ergonomically advanced bed, base, and mattress.
3. Maintain a cool, dark, and quiet bedroom.
4. Keep technology, including phones, out of the bedroom.
5. Avoid consuming caffeine after 4 p.m.
6. Dedicate the hour before bedtime to relaxation activities like reading a book, drinking herbal tea, taking a warm bath, or meditation.

Wrap-Up

In the United States, the average lean body mass is alarmingly low. For instance, the typical 30-year-old male has a lean body mass (LBM) of only 72 percent, while for women of the same age, the average LBM is around 60 percent.

To improve your lean body mass, you must eat for muscle gain and fat loss, follow a resistance training program that works all your muscle fibers, perform three to four calorie-burning cardio sessions weekly, and get 7 to 8 hours of quality sleep each night. 

Do these things consistently, and you will steadily but surely achieve your goal of lean body mass. 

References

1. ACE Insights Blog. (2024, January 26). https://www.acefitness.org/resources/pros/expert-articles/
2. Knutson KL. Impact of sleep and sleep loss on glucose homeostasis and appetite regulation. Sleep Med Clin. 2007 Jun;2(2):187-197. doi: 10.1016/j.jsmc.2007.03.004. PMID: 18516218; PMCID: PMC2084401.

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