THE LARGEST ENDOCRINE ORGAN IN THE BODY

The knowledge of the mechanisms that induce sarcopenia and the ability to prevent or counteract them, therefore, can greatly contribute to the prevention of disability and probably also mortality in the elderly.
— Pratessi, A, et al. 2013

Understanding the complex balance between anabolic & catabolic factors, and how they exacerbate the severity and speed of aging, will be crucial in determining how to best prevent or reverse the effects of Sarcopenia. As human skeletal muscle will secrete a variety of compounds in response to muscular contractions; which are involved in the inflammatory response, sedentary behaviors will support inflammation and an associated 'suppression' of the muscle derived anti-inflammatory response. 

Physical inactivity promotes an unbalance between these substances towards a pro-inflammatory status, thus favoring the vicious circle of sarcopenia, accumulation of fat – especially visceral – and development of cardiovascular diseases, type 2 diabetes mellitus, cancer, dementia and depression, according to what has been called “the diseasome of physical inactivity”.
— Pratessi, A. et al. 2013

Researchers have estimated that the prevalence of Sarcopenia may be as high as 30% > 60 years of age, and 50% > 80 years of age. We've also identified the most important endocrine myokines secreted by muscle as being; IL-6, IL-8, IL-15, Brain Derived Neurotrophic Factor (BDNF) and Leukemia Inhibiting Factor (LIF)

FIGURE 1

Physical activity has a favorable role in the delicate balance between myokines, which is definitively pushed towards a proinflammatory status by a sedentary lifestyle: inflammation, in turn, enhances sarcopenia and accumulation of fat within the context of skeletal muscle, in a vicious circle that decreases muscle strength and further favors physical inactivity.
— Pratessi, A. et al. 2013

As the accumulation of fat tissue will encourage further inactivity, this will in turn support a chronic inflammatory state within the body; which is known to be involved in the generation of a variety of chronic disease states, from insulin resistance, to neurodegenerative disease, to cancer.

The finding that muscles produce and release myokines provides a plausible biological explanation to the observation that exercise influences metabolism and exerts anti-inflammatory effects (1 - 3). According to Pedersen, contracting skeletal muscles release myokines, which work in a hormone-like fashion, exerting specific endocrine effects on visceral fat. Other myokines act locally, i.e. within the muscle, via paracrine mechanisms, working on signaling pathways involved in fat oxidation.
— Pratessi, A. et al. 2013

Science: 1. The Role of Exercise...Defense against Chronic Diseases.

Science: 2. Physical activity...low-level inflammation.

Science: 3. The anti-inflammatory effect of exercise.

Let's zero-in on Interleukin-6, as it appears to be one of the more important muscle derived anti-inflammatory factors released by muscular contractions.  In laboratory studies, mice who are deficient in IL-6 demonstrate high blood sugar & eventually develop mature onset obesity, suggesting that IL-6 is involved in blood sugar homeostasis. IL-6 released via muscular contractions may will help prevent insulin spikes and keep those levels balanced. 

In conclusion, it can be hypothesized that physical activity, by stimulating IL-6 production, counteracts systemic inflammation and modulates glucose and lipid metabolism...this would explain the well-known favorable effects of physical activity towards the diseases associated with a sedentary lifestyle.
— Pratessi, A. et al. 2013

FIGURE 2

As listed above, some of the other factors related to Sarcopenia/chronic disease prevention - such as IL-15 - will contribute to muscle growth & fat oxidation - specifically visceral fat.

Furthermore, BDNF will contribute to the survival & growth of neurons in the brain, and also contribute to the prevention of Alzheimers, Major Depressive Disorder, acute coronary syndromes, and T2 diabetes. BDNF will also activate an enzyme which leads to the oxidation of fat.  The authors conclude that the aging body may be strongly influenced by the balance of chronic sedentary low level systemic inflammation; see FIGURE 2, and the anti-inflammatory effects of muscular contractions; see FIGURE 1.

In this light, healthy aging can be viewed as the ability not only to power the age-associated proinflammatory state, but also to stimulate and potentiate anti-inflammatory mechanisms.
— Pratessi, A. et al. 2013

It's my hope that a continuation of this type of research in the near future will continue to reveal and provide support to the positive effects that exercise might have on the prevention of a whole host of chronic, and previously thought intractable diseases.