Muscle Matters: The Surprising Link Between Sarcopenia and Chronic Disease
As we age, we lose a startling amount of muscle. The rate of deterioration varies from person to person, but it is estimated that we lose about 1-2% of muscle mass per year after the age of 30. This may not sound like much, but over decades, this effect compounds, leading to massive reductions in muscle mass and strength. By the age of 70, the average person will have lost around 30% of their muscle mass [1].
This process, known as sarcopenia, not only diminishes our strength and physical independence, but has serious implications for our risk of chronic diseases due to muscle tissue’s influence on our metabolic and cognitive health.
Without a tangible example, it might be hard to visualize what 1-2% of muscle loss per year actually looks like. The figure below, which was generated through MRI imaging, depicts the thigh muscles of two men in their 70’s. The man in the top image was relatively inactive. The man in the bottom image was a triathlete [2]:
Source: Wroblewski et al, 2011
While the aesthetic difference in the picture above is remarkable, the research literature suggests that muscle isn't just for show. While it is obviously vital to our physical appearance and functional strength, it is also a metabolic organ that plays a key role in our systemic health.
It's relatively intuitive that a loss of muscle mass would be associated with a number of health problems, such as an increased risk of falls, fractures, and disability [3]. But less well known is the link between sarcopenia and chronic diseases such as diabetes, cardiovascular disease, and even cancer.
Sarcopenia and Type 2 Diabetes
Type 2 diabetes is a disease of blood sugar dysregulation. Sarcopenia is linked to type 2 diabetes because muscle tissue plays an important role in regulating blood sugar levels. When we have less muscle mass, our body becomes less efficient at taking glucose out of the bloodstream, which can lead to chronically high blood sugar levels and insulin resistance [4]. This puts us at a greater risk for developing type 2 diabetes. Additionally, the loss of muscle mass can also simply lead to a decrease in physical activity level, which further exacerbates the risk of developing type 2 diabetes.
Sarcopenia and Cognitive Decline
Muscle’s amazing effects on metabolism don’t end with blood sugar control. Compelling research has strongly linked sarcopenia to cognitive decline, and this doesn’t appear to simply be a correlation. Indeed, it turns out that muscle – in addition to contracting to facilitate movement – is also a hormone-releasing organ, sending out a variety of proteins with protective biological functions. Some of these molecules, such as cathepsin B and brain-derived neurotrophic factor, have been shown to cross the blood-brain barrier and promote the growth of new nerve cells in the brain [5]. Other neuroprotective mechanisms relate to muscle’s effect on mitochondrial health, insulin metabolism, and protein metabolism.
The figure below, from a recent review paper from Oudbier and colleagues, shows these mechanisms in detail:
Source: Oudbier et al., 2022
How to Prevent Sarcopenia: A Two-Pronged Approach
The good news is that sarcopenia can be prevented and even reversed in most cases without any expensive pharmaceuticals. The best medicine, in this case, is diet and exercise. Specifically, resistance training and ensuring your diet has sufficient protein.
Resistance Training
In the year 2020, the World Health Organization amended its physical activity recommendations to include muscle strengthening activities at least two days a week for all adults [6]. Whether you’re in your 40's and want to slow the effects of sarcopenia as you age, or you’re in your 70’s and wanting to reverse it altogether, the prescription is clear: you need to strength train. While it’s somewhat harder to build muscle as you age, research shows it’s possible, no matter your age [7].
Resistance training doesn't necessarily mean lifting heavy weights at the gym. It can take the form of bodyweight exercises such as push-ups, squats, lunges, or stairs, as well as resistance training using dumbbells, bands, or machines. The key is to challenge your muscles in a way that gives them the signal to grow.
Starting a strength training program can be intimidating, especially if you are new to exercise. See this article for a few basic tips on how to get started.
Adequate Protein Intake
In addition to resistance training, to preserve muscle, it is also important to ensure your diet has sufficient protein. Protein forms the building blocks of muscle, so it is particularly important for anyone making a concerted effort to build or maintain muscle mass. Nutrition experts recommend that adults consume about 1-2 grams of protein per kilogram of body weight per day [8]. This can come from plants, animals – whatever fits your preferences. For individualized advice, please consult a trusted health professional.
Bottomline
Sarcopenia is a silent killer, affecting a large proportion of the elderly population. While a certain extent of muscle loss is inevitable as we age, research shows that sarcopenia can be prevented and even reversed through regular resistance training and a protein-rich diet. If you build these habits into your wellness lifestyle, you can rest assured that you’re reducing your risk of not only frailty and falls, but also many of the chronic diseases which plague our healthcare system.
References
[1] Keller, K., & Engelhardt, M. (2013). Strength and muscle mass loss with aging process. Age and strength loss. Muscles, ligaments and tendons journal, 3(4), 346.
[2] Wroblewski, A. P., Amati, F., Smiley, M. A., Goodpaster, B., & Wright, V. (2011). Chronic exercise preserves lean muscle mass in masters athletes. The Physician and sportsmedicine, 39(3), 172-178.
[3] Yeung, S. S., Reijnierse, E. M., Pham, V. K., Trappenburg, M. C., Lim, W. K., Meskers, C. G., & Maier, A. B. (2019). Sarcopenia and its association with falls and fractures in older adults: a systematic review and meta‐analysis. Journal of cachexia, sarcopenia and muscle, 10(3), 485-500.
[4] Sayer, A. A., Dennison, E. M., Syddall, H. E., Gilbody, H. J., Phillips, D. I., & Cooper, C. (2005). Type 2 diabetes, muscle strength, and impaired physical function: the tip of the iceberg?. Diabetes care, 28(10), 2541-2542.
[5] Oudbier, S. J., Goh, J., Looijaard, S. M. L. M., Reijnierse, E. M., Meskers, C. G. M., & Maier, A. B. (2022). Pathophysiological mechanisms explaining the association between low skeletal muscle mass and cognitive function. The Journals of Gerontology: Series A, 77(10), 1959-1968.
[6] Bull, F. C., Al-Ansari, S. S., Biddle, S., Borodulin, K., Buman, M. P., Cardon, G., ... & Willumsen, J. F. (2020). World Health Organization 2020 guidelines on physical activity and sedentary behaviour. British journal of sports medicine, 54(24), 1451-1462.
[7] Welle, S., Totterman, S., & Thornton, C. (1996). Effect of age on muscle hypertrophy induced by resistance training. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 51(6), M270-M275.
