In this paper, the authors presented an analytically discussion about energy efficiency of Medium Access Control (MAC) protocols for Wireless Body Area Sensor Networks (WBASNs). For this purpose, different energy efficient MAC protocols with their respective energy optimization techniques; Low Power Listening (LPL), scheduled contention and Time Division Multiple Access (TDMA), are elaborated. They also analytically compared path loss models for in-body, on-body and off-body communications in WBASNs. These three path loss scenarios are simulated in MATLAB and results shown that path loss is more in in-body communication because of less energy level to take care of tissues and organs located inside human body. Then the power model for WBASNs of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and beacon mode is also presented.