Belly Fat Harms Muscle at the Cellular Level

A study of human adipose (fat) cells has found more evidence that visceral body fat found deep in the midsection and around the organs is worse than subcutaneous body fat found just beneath the skin.

By decreasing the expression of genes related to skeletal muscle contraction, the study found that visceral fat cells were more likely than subcutaneous fat cells to contribute to muscle wasting.

Published in the prestigious journal Diabetes, French researchers demonstrated that cells from the visceral fat of obese people decreased muscle growth and caused a state of muscle wasting (1). The effect was significantly more pronounced in visceral fat cells in comparison to subcutaneous fat.

During obesity, the growth of fat cells is associated with inflammation and cell dysfunction. The two most prominent types of fat in the body, visceral fat and subcutaneous fat, differ in their inflammation status (2). Visceral fat is much more of a problem when it comes to obesity-related illnesses and disease (3). In fact, obese people have been noted to have abnormal hormone secretion that leads to disruption of highly metabolic tissues like the liver and muscle (4).

More muscle is protective because it increases metabolism, reduces blood glucose, insulin, and lipid levels (1). Impaired muscle function and degeneration, however, increases with age. Increased amounts of visceral fat in obesity has been proposed to cause metabolic dysfunction due to decreased muscle (5).

Additionally, when the researchers surgically removed visceral fat from obese rats they found that the rats’ muscle tissue increased. The rats also regained insulin sensitivity (5). This recent study sought to identify the specific mechanisms behind visceral fat in worsening muscle wasting, inflammation, metabolic syndrome, and chronic disease such as Type 2 diabetes.

They found that visceral fat cells caused inflammation and atrophy in muscle cells by decreasing gene expression of the main proteins found in muscle. Visceral fat was much more potent at reducing muscle-related gene activity compared to subcutaneous fat.

Additionally, visceral fat significantly increased pro-inflammatory proteins like IL-6 and G-CSF while inhibiting the genes necessary for muscle building. Visceral fat also affected the liver by causing insulin resistance reducing the necessary delivery of nutrients to muscle for growth and repair.

References

  1. Pellegrinelli V, Rouault C, Rodriguez-Cuenca S et al. Human adipocytes induce inflammation and atrophy in muscle cells during obesity. Diabetes 2015;db140796.
  2. Cancello R, Tordjman J, Poitou C et al. Increased infiltration of macrophages in omental adipose tissue is associated with marked hepatic lesions in morbid human obesity. Diabetes2006;55:1554-61.
  3. Jensen MD. Role of body fat distribution and the metabolic complications of obesity. J Clin Endocrinol Metab 2008;93:s57-s63.
  4. Harwood HJ. The adipocyte as an endocrine organ in the regulation of metabolic homeostasis. Neuropharmacology 2012;63:57-75.
  5. Borst SE, Conover CF, Bagby GJ. Association of resistin with visceral fat and muscle insulin resistance. Cytokine 2005;32:39-44.
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