Obese individuals often talk about having an insatiable appetite. Even when they are not hungry, they say that the first bites trigger their intense desire for food. They also experience prolonged feelings of unsatisfied hunger after eating. Hunger is a physiological mechanism in which the body signals that we need food supply. However, pathological impairment of this physiological alarm may lead to severe metabolic diseases. It seems that at least one of the mechanisms involved in the etiology of obesity is the disruption of appetite regulation in the bodies of obese individuals.

Feelings of satiety and appetite are precisely regulated by the complex interplay of the nervous and hormonal systems. The hypothalamus, limbic regions, and cerebral cortex are involved in regulating food cravings and feelings of fullness. However, the hypothalamus plays a primary role in regulating appetite.

Hormones such as insulin, leptin, ghrelin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and cholecystokinin (CCK) play a role in satiety and appetite control in coordination with the central nervous system. Ghrelin stimulates appetite, while PYY, PP, GLP-1, and oxyntomodulin inhibit appetite.

It has recently been shown that microbes residing in the gastrointestinal tract also play an important role in regulating appetite. They influence the energy balance and eating behaviors by impacting the gut-brain axis. Some microbial metabolites such as butyrate regulate hormones that control satiety. Some other products of gut microbiota such as neurotransmitters directly affect hypothalamus neurons. Imbalance of gut microbiome called dysbiosis, may lead to the impairment of normal........

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