Wireless Body Area Network (WBAN) is a recent technologically advanced sub-category of Wireless Sensor Networks (WSN) which consists of many bio-sensors, attached in and around of human body, for monitoring the health-related issues from remote places. Energy conservation in WBAN has always been the most crucial issue for the sensor nodes, which are powered by limited capacity battery sources. During sensing and communication, sensing elements emit high temperature from its circuit and transmitting antenna due to inefficient data routing designs. This energy may lead to form hot-spot, which affects the human tissues at a different level. So designing an energy-efficient routing protocol is a very challenging issue to reduce the high emission of temperatures. Different energy-efficient routing protocols have been projected in this survey over the years. The energy-efficient routing protocols endeavor to prolong the network lifetime by minimizing the energy consumption in each deployed nodes. There have been a variety of survey papers put forwarded by researchers to evaluate the performance and categorize the different energy-efficient routing protocols for WBANs. This paper describes an overview of WBAN, a systematic survey of existing contracts for routing and open research issues are discussed.