Beyond BMI: Understanding Lean Body Mass for a Healthier You

By INFS Faculty

2 min read

10 Feb 2023

When people want to lose weight, their goal is often to shed body fat. However, it is important to understand that body weight is made up of more than just fat. In addition to fat, body weight includes water, muscle, and bone.

It is often assumed that a person with a normal Body Mass Index (BMI) is healthy, but this is not always the case. For example, a person with a BMI in the overweight category could have more muscle mass than fat mass. So, although he is healthy, the BMI scale would indicate otherwise. This is why it is important to understand the difference between body weight (used in BMI) and lean body mass.

Lean Body Mass is the total weight of the body less the weight of fat in the body. That means, Lean Mass includes weight of water, organs, bones, and muscle (muscle mass) in the body. Lean Body Mass is also termed as ‘Fat-free Mass’.

To calculate lean body mass, you can use the equation:

Lean Body Mass = Total Body weight – Fat mass.

where ‘Fat Mass’ is also referred to as Percentage of Body weight and called ‘Body Fat Percent’.

For example,
Consider a person weighing 80 kg with 30% body fat.

Their fat mass can be calculated to be (80 × 30%) 24 kg.

To get Lean Mass, we reduce fat mass from total body weight, (i.e. 80 – 25kgs) = 56 kg.

Another method to calculate LBM is using height and weight (Hume,1966).

For men,
LBM = 0.32810 × W + 0.33929 H – 29.5336
For women,
LBM = 0.29569 × W + 0.41813 H – 43.2933

There are also more accurate, but expensive methods to measure body fat percentage, such as BCA analysis, hydrostatic weighing, and DEXA scans.

It is important to focus on increasing lean body mass because gains in muscle mass through proper nutrition and resistance training can have a positive impact on metabolism and overall health. In addition, lean body mass, particularly muscle mass, is crucial for maintaining bone mineral density and preventing bone disorders such as osteoporosis (Ho-Pham et al., 2014).

In conclusion, incorporating physical activity and maintaining lean body mass through muscle building and proper nutrition, especially adequate protein intake, can have a positive impact on overall health and well-being for a lifetime.

References

Cheung, C.-L. et al. (2021) ‘Systematic review and meta-analysis of lean mass and mortality: Rationale and study description’, Osteoporosis and Sarcopenia, 7, pp. S3–S12. doi: 10.1016/J.AFOS.2021.01.001.
Ho-Pham, L. T., Nguyen, U. D. T. and Nguyen, T. V. (2014) ‘Association Between Lean Mass, Fat Mass, and Bone Mineral Density: A Meta-analysis’, The Journal of Clinical Endocrinology & Metabolism, 99(1), pp. 30–38. doi: 10.1210/JC.2013-3190.
Hume, R. (1966) ‘Prediction of lean body mass from height and weight.’, Journal of clinical pathology, 19(4), pp. 389–391. doi: 10.1136/jcp.19.4.389.
Wolfe, R. R. (2006) ‘The underappreciated role of muscle in health and disease’, The American Journal of Clinical Nutrition, 84(3), pp. 475–482. doi: 10.1093/AJCN/84.3.475.

Frequently Asked Questions

1. What is considered a healthy percentage of lean body mass?

A healthy percentage of lean body mass varies depending on factors such as age, gender, and fitness level. Generally, a higher percentage of lean body mass is associated with better metabolic health and overall well-being.A healthy percentage of lean body mass typically falls within the range of 70% to 90%, indicating lower body fat percentages ranging from 10% to 30%. Athletes often aim for even leaner body compositions, with body fat percentages ranging from 7% to 22% for optimal performance. Men typically have higher lean mass percentages, ranging from 80% to 90%, while women tend to fall within the 70% to 85% range.

2.Can you gain lean body mass without gaining weight?

Yes, it's possible to gain lean body mass without necessarily gaining weight, especially if you're simultaneously losing fat mass. This process, known as body recomposition, involves building muscle while reducing body fat through targeted exercise and nutrition.

3. Is it possible to increase lean body mass as you age?

Yes, it's possible to increase lean body mass even as you age, although it may require more effort and consistency compared to younger individuals. Resistance training, adequate protein intake, and overall lifestyle factors play key roles in preserving and building muscle mass.

4. What role does genetics play in determining lean body mass?

Genetics can influence an individual's predisposition to certain body types and muscle development. While genetics may play a role in determining baseline muscle mass, lifestyle factors such as diet and exercise still significantly impact lean body mass.

5. Can certain medical conditions affect lean body mass?

Yes, certain medical conditions, such as hormonal imbalances, chronic illnesses, or prolonged periods of inactivity, can affect lean body mass negatively. Managing these conditions and adopting a healthy lifestyle can help preserve or improve lean body mass.

6. How does diet impact lean body mass?

Nutrition plays a crucial role in supporting lean body mass, particularly protein intake, which provides the building blocks for muscle repair and growth. A balanced diet rich in protein, healthy fats, and complex carbohydrates supports muscle development and maintenance.

7. What are the best exercises for increasing lean body mass?

Resistance training exercises, including weightlifting, bodyweight exercises, and resistance bands, are highly effective for increasing lean body mass. Compound movements targeting multiple muscle groups, such as squats, deadlifts, and bench presses, are particularly beneficial.

8. Can supplements help increase lean body mass?

While supplements can complement a balanced diet and exercise regimen, they should not replace whole foods. Protein supplements, creatine, and branched-chain amino acids (BCAAs) are commonly used to support muscle growth, but their effectiveness may vary based on individual needs and preferences.

9. How long does it take to see changes in lean body mass with exercise?

The timeline for seeing changes in lean body mass varies depending on factors such as genetics, exercise intensity, and nutrition. Generally, noticeable improvements in muscle mass may occur within a few weeks to several months of consistent training.

10. Can stress or lack of sleep affect lean body mass?

Yes, chronic stress and inadequate sleep can negatively impact lean body mass by increasing cortisol levels, which can lead to muscle breakdown and hinder muscle recovery. Prioritizing stress management techniques and quality sleep is essential for preserving muscle mass.

11. Is it possible to lose lean body mass while trying to lose weight?

Yes, it's possible to lose lean body mass, particularly if weight loss occurs rapidly or if diet and exercise strategies are not optimized to preserve muscle mass. To minimize muscle loss during weight loss, focus on gradual weight loss, prioritize strength training, and consume adequate protein.

12. Can lean body mass affect metabolism?

Yes, lean body mass significantly influences metabolism, as muscle tissue is metabolically active and requires more energy at rest compared to fat tissue. Increasing lean body mass through resistance training can boost metabolism and support weight management efforts.

13. What are the risks of having low lean body mass?

Low lean body mass, often indicative of muscle wasting or sarcopenia, can increase the risk of frailty, falls, and functional limitations, particularly in older adults. Maintaining or increasing lean body mass is essential for preserving mobility, independence, and overall quality of life.