Muscles are visually pleasing, but they also have a deep inner beauty you should know about.
Skeletal muscle is versatile, playing a critical role in movement, posture, breathing, circulation, and temperature regulation. Less known is muscle’s ability to support energy and protein metabolism. These features have tremendous influence over our health.
What Muscle Is Made Of
Muscle is a tissue composed primarily of proteins, representing nearly 75% of all protein in our body (1). Proteins are bound up chains of smaller components, called amino acids, linked together in various sequences. When we eat dietary protein, these chains are broken down into amino acids and used for various functions like forming enzymes and hormones, aiding in cellular processes, and building tissue.
Muscle Protein Synthesis and Muscle Protein Breakdown
Our bodies are in a constant state of protein turnover where amino acids are used to build up proteins and proteins are broken down to release amino acids. In relation to muscle, we term these processes muscle protein synthesis (MPS) and muscle protein breakdown (MPB), respectively.
More MPB occurs when energy demands are high or supplies are low, such as during malnutrition (1). A state of prolonged MPB is associated with poor health.
Age, Illness, and Muscle Loss
Muscle is crucial for recovery from illness. It helps balance metabolic needs and acts as a reserve of protein for energy. As a result, muscle decreases in size during sickness. This process is especially prevalent in older individuals who do not address muscle loss with nutrition and exercise.
Unfortunately, the role of muscle throughout life is underappreciated, as is its importance in preventing obesity and diabetes. There is abundant evidence that points to the role of altered muscle metabolism in these chronic diseases (2-4).
This may be explained by how our bodies handle glucose. Muscle is the most abundant insulin-sensitive tissue and helps maintain healthy glucose levels (5,6). Loss of muscle mass associated with disuse, disease, and aging may be fundamental to metabolic dysfunction. This can lead to a host of metabolic derangements, including reduced insulin signaling, fat tissue expansion, and increased levels of inflammation and reactive oxygen species (7).
Basically, muscle loss is not good for overall health, causing scientists to call for increased protein intake and routine exercise to optimize muscle metabolism (2).
More Muscle, More Energy Expenditure
Even relatively small differences in muscle mass can have a significant effect on energy balance. For example, every 10-kilogram (22-pound) difference in lean mass translates to a difference in energy expenditure of approximately 100 calories burned per day.
Considering how obesity often develops over longer periods of time, an extra energy expenditure of 100 calories per day translates to a loss of nearly 5 kilograms (11 pounds) of fat mass per year (2).
For this reason, maintaining muscle mass can contribute to the prevention of obesity. Not only will muscle make you look better, but it will keep you feeling better, too.
- Argilés JM, Campos N, Lopez-Pedrosa JM, et al. Skeletal Muscle Regulates Metabolism via Interorgan Crosstalk: Roles in Health and Disease. J Am Med Dir Assoc. 2016 Sep 1;17(9):789-96.
- Wolfe RR. The underappreciated role of muscle in health and disease. Am J Clin Nutr. 2006 Sep;84(3):475-82.
- Müller MJ, Lagerpusch M, Enderle J, et al. Beyond the body mass index: tracking body composition in the pathogenesis of obesity and the metabolic syndrome. Obes Rev. 2012 Dec;13 Suppl 2:6-13.
- Park BS, Yoon JS. Relative skeletal muscle mass is associated with development of metabolic syndrome. Diabetes Metab J. 2013 Dec;37(6):458-64.
- Baron AD, Brechtel G, Wallace P, et al. Rates and tissue sites of non-insulin- and insulin-mediated glucose uptake in humans. Am J Physiol. 1988 Dec;255(6 Pt 1):E769-74.
- DeFronzo RA, Jacot E, Jequier E, et al. The effect of insulin on the disposal of intravenous glucose. Results from indirect calorimetry and hepatic and femoral venous catheterization. Diabetes. 1981 Dec;30(12):1000-7.
- Stump CS, Henriksen EJ, Wei Y, et al. The metabolic syndrome: role of skeletal muscle metabolism. Ann Med. 2006;38(6):389-402.
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