The leptin, which is poly peptides hormones secreted mainly from fat cells, is considered anorexigenic. Leptin inhibits appetite by causing chemical signals after combining with its specific receptors in the hypothalamus area. These signals can be discovered by variation of the concentration of the hypothalamus proteins P.STAT3 (Phospho Signal Transducer and Activator of Transcription) P.MAPK( Phospho Mitogen-Activated Protein Kinase), which can be inhibited by negative feedback of PTP1B( Phospho Tyrosine Phosphatase 1 ) or SCSO3( Suppressor of Cytokine Signaling), resulting in homeostatic and energetic regulation in the body. Moreover, there are signals disorders cases, which lead to obesity in spite of increased plasma level of leptin, which indicates to existence of leptin resistance.