Important Facts About Lean Muscle and Body Fat

The body is an amazing organism made up of different elements, including various types of tissue, bone, organ and fluid. Two of which, lean muscle and body fat, are discussed most often when it comes to exercise and living a sustainable lifestyle. We exercise and monitor our nutritional intake in order to build one, lean muscle, while trying to lose the other, body fat (also known as adipose tissue).

How Much Lean Muscle Does the Average Adult Carry?

Skeletal muscle is the most abundant tissue in our body, accounting for approximately 42 and 35 percent of body weight in men and women respectively. In other words, an average male weighing 185 pounds has about 78 pounds of lean muscle tissue while a female weighing 140 pounds has approximately 49 pounds of lean muscle tissue (note: this is not an “exact” number). Take muscle and fat out of the equation, and bodyweight still has other constituents like, water, mineral, bone, connective tissue, and organ weight. Speaking of organ weight, did you know the average human heart weighs about 10 ounces while the brain weighs about 3 pounds? That same average male may have, on average, about 25 percent body fat (or “about” 46 pounds of fat) while that average female may have 30 percent body fat (or “about” 42 pounds of fat).

Did You Know this About Lean Muscle

One of the amazing things about muscle tissue is it has the ability through progressive overload, to increase in size (known as muscle hypertrophy). Donnelly and colleagues have reported that strength training studies (lasting from 8 to 52 weeks) have shown increases of 2 to 5 pounds of muscle mass. In addition to increasing in size, muscle tissue also gets stronger with prolonged training. A periodized strength training program can elicit changes in endurance capacity, power output and force production while keeping sarcopenia at bay.

Protein stores found in muscle can account for about 30,000 calories of energy. Muscle tissue can contribute approximately 20 percent of the body’s total daily energy expenditure compared to 5 percent for fat tissue (it would be great if we could tap into those fat stores more often).

Lean muscle tissue requires 3-4 times more calories to maintain compared to fat and is important in the process of energy metabolism. A pound of metabolically active muscle tissue requires 5-7 calories per pound to maintain while less active fat tissue, requires only 2 calories per pound.

Finally, lean muscle plays an important role in the aging process. With advancing age we experience a loss of exercise capacity. This is due to first, to a decline in skeletal muscle mass and strength during aging and then a decrease in maximal oxygen uptake mainly due to a drop in maximal heart rate, according to Henning Wackerhage, PhD, a Senior Lecturer in Molecular Exercise Physiology at the University of Aberdeen.

Did You Know this About Fat

Fat is found in the body in the form of triglycerides and stored in fat cells which are called adipocytes. According to Coyle, about 50,000 to 60,000 calories of energy are stored in fat cells throughout the body. Fat can also be stored within skeletal muscle cells.

Fat accumulated in the lower body is subcutaneous. While fat in the abdominal area is largely visceral. Where fat ends up on your body is influenced by several factors, including hormones and heredity.

The photo below shows equivalent amounts of fat and muscle. Lean muscle, however, is more dense and takes up one-third less space compared to fat. Five pounds of muscle and fat may in fact weigh the same but that is where the similarities end.

One thing is for certain, everyone wants more lean muscle and less body fat. Regular strength training is a much needed critical component for everything from health to activities of daily living. Check out some of the many great strength training routines found on Jefit, like the FitBody Plan. Stay strong with Jefit.

References

Marieb, EN and Hoehn, K. (2010). Human Anatomy and Physiology (8th ed.). San Francisco: Benjamin Cummings.

Elia, M. (1999). Organ and Tissue Contribution to Metabolic Weight. Energy Metabolism: Tissue Determinants and Cellular Corollaries. Kinney, J.M., Tucker, H.N., eds. Raven Press. New York.

Donnelly, J.E., Jakicic, J.M., et. al. (2003). Is Resistance Training Effective for Weight Management Evidence-Based Preventive Medicine. 1(1): 21-29.

Wackerhage, H. (2014). Molecules, Aging and Exercise in Molecular Exercise Physiology. Routledge.

Wood, M. (2018). TBC30: 6 Steps to a Stronger and Healthier You. Wicked Whale Publishing, 2nd edition.

Coyle, EF. (1995). Fat metabolism during exercise. Sports Science Exchange, 8(6):59.

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