Excess visceral fat tissue is demonstrably harmful to long term health; overweight people have a higher risk of age-related disease, higher lifetime medical costs, and a shorter life expectancy. The more overweight, the worse the prognosis. One of the noteworthy mechanisms by which fat tissue leads to harm is the generation of chronic inflammation via the activities of fat cells. Inflammation spreads widely in the body, disrupting cellular metabolism and accelerating the progression of all of the common age-related diseases.
What causes this inflammation? One mechanism is that fat cells produce signals, inflammatory cytokines for example, that rouse the immune system to what is ultimately useless activity. Some of the signal molecules secreted by fat cells overlap with those produced by cells suffering infection. When fat cells die, they produce forms of debris that spur inflammatory reactions. Macrophages are the cells responsible for cleaning up this sort of waste material, and it has been shown that fat tissue is rich in macrophages with an inflammatory polarization.
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