Why can exercise build muscle and reduce fat?

Muscles are the armor of the human body. If we use a car as an analogy, they are like the sheet metal of a car. Muscles are involved in maintaining body posture, performing movements, and regulating breathing. However, in addition to being related to exercise, muscles also play an important role in the regulation of blood sugar and fat, and the pathological mechanisms of chronic diseases (such as obesity and diabetes).

We all know that the so-called Adipokines are mainly used to refer to cytokines secreted by adipose tissue, while Myokines are used to refer to cytokines secreted by muscles (temporarily translated as muscle hormones). Many studies have pointed out that Myokines have autocrine, paracrine, and endocrine effects. During exercise, muscles contract and secrete myokines, which affect other organs such as bones, pancreas, intestines, liver, white adipose tissue, brown adipose tissue and brain.

Studies have found that there are hundreds of myokines, some of which can act directly on the muscles themselves (Autocrine), such as BDNF (Brain-derived neurotrophic factor) and IL-6 (interleukin-6). These two myokines are also involved in fat oxidation regulated by AMPK (AMP-activated protein kinase).

LIF (Leukaemia inhibitory factor), IL-4, IL-6, IL-7 and IL-15 can cause muscle hypertrophy; IL-6 and IL-15 can also stimulate the decomposition of fat, especially abdominal fat. Myostatin inhibits muscle hypertrophy, but through exercise, the liver will secrete the so-called Follistatin, which itself has the effect of inhibiting Myostatin.

IL-6 will be discussed in particular here. IL-6 is mainly secreted by T cells, macrophages, B cells and skeletal muscle cells. Early studies suggested that exercise causes local muscle damage, and the immune system responds by secreting IL-6. However, current research suggests otherwise! It is believed that IL-6 is mainly secreted by muscles during exercise; the longer the exercise time and the more muscles involved, the higher the IL-6 secreted by the muscles, and the concentration can even be 100 times higher than usual!

IL-6 secreted by exercising muscles enhances (insulin-stimulated) cellular uptake of glucose and stimulates the liver to output glucose. IL-6 also stimulates the intestinal L cells to secrete glucagon-like peptide 1 (GLP-1), further promoting insulin secretion.

IL-6 also has anti-inflammatory effects and inhibits the production of tumor necrosis factor (TNF). When IL-6 levels rise, the levels of anti-inflammatory cytokines IL-1ra and IL-10 will also increase. IL-6 also stimulates the production of cortisol, indirectly leading to neutrocytosis and lymphopenia.

Other myokines, such as IL-8 and CXCL-1, may enhance aniogenesis. IGF-1, FGF-2 and TNF-β are related to bone formation. Follistatin-related protein 1 improves endothelial cell function and revascularization of ischemic muscle. Irisin increases during exercise and has effects on both brown and white adipose tissue, primarily increasing energy expenditure.

Myokines’ role is so complex! This also explains why exercise, in addition to building muscle and reducing fat, also has the effect of reducing the risk of chronic diseases (such as type 2 diabetes). In addition, because muscles affect other organs through myokines, some scholars believe that muscles should also be considered endocrine organs!

Two thousand years ago, Hippocrates, the father of medicine, once said: "Walking is the best medicine." This statement is probably only half right! Because drugs are divided into Taiwan X drugs and original O drugs, and exercise must actually exercise the muscles to be a top-notch special medicine.

This article comes from: Ye Junyuan's Healthy Factory

※For more information, please visit Dr. Yeh Jun-kwan’s blog