Obesity as an infectious disease– review of the literature
Obesity, which is a pathological and excessive accumulation of body fat (WHO; World Health Organization), is the problem undertaken in the world literature for several decades. Significant mortality due to the obesity comorbidities is the basis to undertake an intensive work on the new preventive and therapeutic strategies worldwide. Nevertheless, due to the multifactorial origin of obesity and the growing number of obese subjects, the effectiveness of these strategies appears to be highly limited. Besides to the traditionally recognized etiological factors of obesity, many reports showing an association of infectious agents and uncontrolled weight gain have been published recently. In this paper we present an overview of reports confirming the association between infections and obesity. Data showed that a specific viral and bacterial infections as well as infections with protozoa and prions are associated with the increased intracellular accumulation of lipids, hypertrophy and hyperplasia of adipose tissue, body weight gain, increase of BMI and changes in lipid metabolism. These infections can serve as direct causal agents, but they can also interact with other environmental factors, thus increasing the predisposition to the development of obesity. There are at least a few hypotheses on the pathogenesis of “infectobesity.” There are some reports describing the damage of the central nervous system and hence the endocrine glands dysfunction due to infection, increased insulin susceptibility of infected cells, reduced production and release of leptin, increased glucose and fatty acids transport into adipocytes and inflammatory basis for infectobesity. Undoubtedly, awareness of the relationship between infections and obesity brings us closer to develop the effective preventive and therapeutic strategies, but it also raises the question about other, so far underestimated, environmental factors that increase the predisposition to obesity.