Body Composition And Lean Body Mass

Body Composition and Lean Body Mass

The body composition is a set of elements that make up the human body. Among the elements are fat mass, muscle mass, amount of water, skeleton, and organs. Together they make up the body. Measuring these components in this way is, therefore, a good indicator of health.

Body fat is essential for maintaining body temperature, as well as protecting joints and internal organs. Body composition analyzers allow you to monitor your body fat. The energy or calories that our body needs come from what we eat and drink. This energy is burned by our physical activity and the functioning of our bodies. By consuming several calories equal to the calories burned, all of the calorie intakes are converted into energy. But with more calories being consumed than the amount burned, the excess calories are stored in fat cells. If this fat store is not then converted into energy, it creates excess body fat. Even though you need healthy body fat, excess fat can be detrimental to your long-term health.

Body Composition And Lean Body Mass

What is Lean Body Mass?


The lean body mass indicates the muscle volume of the body. The fat mass of the body when subtracted from the overall body weight gives the lean body mass. It can be used to check the progress made during weight training sessions or to initiate a change in diet. For ambitious or professional strength athletes, lean body mass replaces Body Mass Index (BMI), which is irrelevant for muscular people. BMI is more suitable for people with little muscle and is only a first comparison. The Lean Mass Index, on the other hand, is better suited to athletes who train regularly and provides a much more relevant analysis of body condition. (1)

Healthy Levels:

Lean mass makes up about sixty to eighty-five percent of body mass in healthy persons. However, this value greatly depends on the gender, age, and fitness of the subject. The proportion of lean body mass is higher in young adults as compared in old people and men than in women.

Lean Body Mass and Gender:

Lean body mass provides a good relationship between the overall weight and the fat-free mass of the body in young adults. Many research articles have been published that investigate the variations in the lean body mass of both genders.

According to a paper published in PubMed, body composition varies by gender. In research that included 94 men and 114 women of similar mean ages, it was found that the composition of the body includes more lean mass in men than in women. In contrast, the women had more overall fat mass, due to more fat storage locations in the body. (2)

Lean Body Mass and Aging:

The loss of muscle mass with advancing age has been commonly called sarcopenia. Sarcopenia is distinct from muscle wasting, which, in general, refers more to the involuntary loss of lean body mass due to age-related wasting of the muscles due to decreased activity and other reasons. The percentage of fat mass that is lost also increases with aging. (3)

Average Lean Body Mass in Americans:

Due to better hygienic conditions, better nutrition, and a healthy lifestyle, most Americans have a lean body mass that falls between the healthy ranges. The lean body mass of any person depends a lot on nutrition, and protein-filled foods along with “good” fat content can help you get rid of the fatty kilograms that act to decrease your lean body mass.

The average lean body mass varies by gender and age in Americans. On average, most American men have a lean body mass that falls between 75 percent and 86 percent. On the other hand, most American women have an average lean body mass of 69 to 76 percent of their total body weight. Considering the global trends, the average lean body mass in Americans falls in the healthy range. (4)

Lean Mass, Body Composition, and Weight Control:

Everyone should realize that too much fat is unhealthy. It increases the required basal metabolic rate, it weakens the heart, muscles, and organs. Trans fats increase blood sugar and have already led to high blood pressure or organ damage. The diseases that a body fat percentage can bring with it are numerous.

Having above-healthy weight sounds like the alarm bells. In the long term, health problems can develop in some people, such as cardiovascular disease, high blood pressure, and diabetes. It is recommended to lose weight and strive towards developing a good body composition.

Decreasing the fat mass of the body can have a lot of benefits. Decreasing the fat mass leads to a decreased cholesterol level in the body, which directly translates to decreased risks for cardiovascular events and strokes. Moreover, increasing the lean muscle mass of the body through a proteinaceous diet is also beneficial in a way that a muscular body has a good appearance as compared to a fat-laden body.

(5) Conversely, a level of body fat that is too low can lead to osteoporosis at an older age, irregular periods, and even possible infertility.

Why Building Lean Body Mass Matters?

Body Composition And Lean Body Mass

Lean Body Mass Combats Obesity:

Obesity is a chronic metabolic disorder that is associated with a high risk of many other disorders associated with vital body systems such as CNS or CVS. A person having a body mass index of 25 or more is considered overweight by medical science. However, a person cannot be considered obese if he or she has a BMI of less than 30.

Having a higher lean body mass to overall body mass ratio indicates that the majority of the body weight is taken up by the building blocks of the body i.e, proteins. On the other hand, having more fat mass contributes to obesity, which results in a variety of problems for the subject. Having more protein content in the body as compared to the fat content not only helps in building the muscles but also helps to fight obesity as the muscle cells, even when at a resting state, require a considerable number of calories to function properly. On the other hand, the fat cells serve as a storage site for the fat, so they do not require any considerable calories at rest. Having more lean body mass, therefore, helps to combat obesity as more lean body mass means more muscle and less fat cells to store fat. (6)

Helps Fight Disease and Illness:

Almost every metabolic reaction occurring inside our bodies, whether it be immunity, digestion, or any other reaction, requires protein of some form that helps boost up that reaction (enzyme) or directly has a protein involved. This clears out the importance of protein in maintaining the body’s reactions.

Lean body mass is all about protein; having more lean body bass means that you have a more muscular body. this means that you have more muscles available, which directly means that you have enough protein available to cater to all the body’s needs. Disease or illness requires a lot of protein to heal, as almost every immune reaction and the wound healing process has some kind of protein attached to it. Therefore, having more lean body mass can help to counter disease and help the wounds heal more efficiently. (7)

Helps build strong bones:

Regular muscle training strengthens and supports the skeleton by increasing the muscle mass of the body. This also promotes a sense of balance and is good fall prevention. This can reduce the risk of fractures. Muscles and bones are closely related – fewer muscles mean less bone stability. This is because bone stability is directly related to the amount of tension being exerted on them by the muscles of the body.

Higher muscle mass means that there is more tension on the bones, which supports and promotes healthy bone remodeling in the person. When the bones are subjected to increased tension from the muscles, stronger remodeling makes them resistant to fractures and strengthens the whole skeleton. (8)

Lean Body Mass and Insulin Resistance:

Diabetes is a metabolic disease characterized by a chronic, abnormal elevation in blood sugar, defined by the level of sugar in the blood. This increase in blood sugar is caused by a dysfunction in the secretion or action of insulin, a hormone made by the pancreas. It can cause long-term damage to various vital organs of the body and can cause nephropathy, neuropathy, or retinopathy.

The increase in muscle glucose utilization observed with increased lean body mass is made possible by the increase in transmembrane glucose transport by essentially non-insulin-dependent mechanisms. This increase in muscle glucose use induces a significant decrease in blood sugar without however the occurrence of hypoglycemia. Research has also indicated that increasing the skeletal muscle mass helps to reduce insulin resistance in people who are prone to diabetes. (9)

Calculating the Lean Body Mass:

The formula for the calculation of lean body mass is:

Lean Body Mass (LBM) = Total Body Weight (TBW) – Total Fat Mass

Seeing the formula above, one can see why lean body mass is also sometimes called the “fat-free mass” of the body. Lean body mass is made up of three components, two of which are water. Everything else is lumped together in what’s called your “lean dry mass,” which includes your bone minerals, protein content, and so on.

Using the Fat Percentage to Calculate Lean Body Mass:

Body fat percentage can help you calculate your lean body mass through the following formula:

Lean Body Mass (LBM) = Total Body Weight (TBW) – (TBW x Fat Percentage)

Multiplying the total body weight with fat percentage gives you your fat mass, which can be subtracted from total body weight to calculate the lean body mass.

How to Measure Fat Percentage:

Skinfold Assessment:

Getting a skinfold assessment using three, four, or seven different sites on the body is considered the most convenient method of estimating the body fat percentage. The procedure is carried out by a professional who pinches the skin and measures the thickness of the skinfold at each site where the body fat measurement is being made.

Body Composition And Lean Body Mass

Each protocol has specific test sites, typically located on the chest, arms, abdomen, and thighs.

After having introduced the figures in an equation, the body fat percentage can be calculated from the formula of Durnin and Womersley where: IMG = (495 / (C – (M x log (sum of the 4 skinfolds)))) – 450, the practitioners can estimate the percentage of body fat.

Bioelectrical Impedance Analysis:

Bioelectrical impedance analysis is a device designed to estimate body composition based on the different conductive properties of different body tissues. The BIA devices all work by sending tiny electrical impulses through the body and measuring the rate of return of these impulses.

Since muscle tissue conducts electrical impulses faster than fat tissue (made up of less water), a body with less fat will return a response faster. The body fat percentage can be then calculated.

Hydrostatic Weighing:

Hydrostatic weighing is also known as underwater weighing. The hydrostatic weighing procedure involves comparing a person’s normal body weight to their body weight when submerged under the water. Using the weights obtained by weighing the subject under and above the water and the density of the water, the professionals can determine the subject’s body fat percentage and density. This number is then used to estimate body composition and body fat percentage.

Lean Mass, Muscle Mass and Body Fat Mass: In a Nutshell

The fat-free mass or the lean body mass is the mass in the body that is not made up of fat. This includes muscles as well as organs, bones, water, tendons, ligaments, blood, nerves, etc. The fat-free mass makes up about 65 to 85% of the total body mass. This depends on age, gender, and individual fitness level. In extreme cases, it is also below or above this range.

Another important indicator is muscle mass, which accounts for the size of muscles of your body. Muscle mass matters considerably, as more muscle mass means that you have greater protein content in your body to spare. Fat mass is just the total body weight taken up by fat.


  1. Welcome to GymNation. (2021). Retrieved 12 November 2021.
  2. Schorr, M., Dichtel, L., Gerweck, A., Valera, R., Torriani, M., Miller, K., & Bredella, M. (2018). Sex differences in body composition and association with cardiometabolic risk. Biology Of Sex Differences, 9(1).
  3. Boutari, C., & Mantzoros, C. (2017). Decreasing Lean Body Mass with Age: Challenges and Opportunities for Novel Therapies. Endocrinology And Metabolism, 32(4), 422.
  4. The Average Lean Body Mass | LIVESTRONG.COM. (2021). Retrieved 12 November 2021.
  5. Willoughby, D., Hewlings, S., & Kalman, D. (2018). Body Composition Changes in Weight Loss: Strategies and Supplementation for Maintaining Lean Body Mass, a Brief Review. Nutrients, 10(12), 1876.
  6. Brady, S. (2021). 5 Important Reasons To Maintain Lean Body Mass As You Age – Virginia Therapy & Fitness Center. Virginia Therapy & Fitness Center. Retrieved 12 November 2021.
  7. Lang, T. (2011). The Bone-Muscle Relationship in Men and Women. Journal Of Osteoporosis, 2011, 1-4.
  8. Srikanthan, P., & Karlamangla, A. (2011). Relative Muscle Mass Is Inversely Associated with Insulin Resistance and Prediabetes. Findings from The Third National Health and Nutrition Examination Survey. The Journal Of Clinical Endocrinology & Metabolism, 96(9), 2898-2903.