In recent years the incidence of obesity has become significantly greater and consequently there was an increase in the incidence of associated comorbidities such as diabetes mellitus, ischemic heart disease, stroke and cancer. According to the WHO (World Health Organization) as much as 35% of adults are overweight, and 11% of the world population is obese. Understanding of the physiological process of feeding and appetite regulation is important for understanding the regulation of appetite disorders leading to obesity, which can lead to solving this problem through the development of therapies. The regulation of appetite occurs via gut-brain axis. The axis links the gastrointestinal (GI) tract with appetite regulation centers in the brain via the endocrine and neural components. Neural component consists of fiber vagus nerve that conveys information to the brainstem, and the endocrine component consists of hormones secreted from the GI tract that transmit information to the arcuate nucleus (ARC) of the hypothalamus. The hypothalamus plays a key role in the integration of information and the regulation of appetite. GI hormones are secreted from the GI tract in response to the input of nutrients. The most important hormones in the regulation of appetite are GLP-1, PYY, PP and OXM which effect anorexigenic (those that reduce appetite) ARC neurons, and thus cause a feeling of satiety and, consequently, a decrease in appetite. The only orexigenic hormone is ghrelin, which stimulates orexigenic (those that increase appetite) population of ARC neurons of the hypothalamus and increases appetite. New insights on the GI hormones create the opportunity to develop a successful obesity treatment that can help in weight loss along with life's changes.