The Wireless Body Area Networks (WBAN) is an emerging type of real-time monitoring used in the healthcare sector. It has the potential to revolutionize the healthcare sector by allowing patients not to physically visit doctor clinics or hospitals for medical checkups. But implementing such a system is challenged by many factors. The most important one is energy consumption. Energy consumption of all nodes in general and that of the gateway node in particular is critical. The gateway node is responsible for conveying sensor information to medical servers or doctors. Failure of the gateway node means failure of the overall WBAN system of a patient. Thus, extending the life time of the gateway node is a desirable objective in designing WBAN systems. As energy consumption is directly related to the end-to-end delay, Packet Delivery Ratio (PDR) and medium accessibility rate. So, placement on the human body in a location that is affected the least by delay and has high PDR and medium accessibility should be chosen as the placement location for the gateway node. In this paper, we identify the optimal placement location on the human body for a gateway node in terms of end-to-end delay, PDR, and back-off duration period.