Motivated by the increasing need for improved healthcare solutions, wireless body area networks (WBANs) have shown their great potential in revolutionizing the next generation healthcare through enabling continuous monitoring of health status with early detection of abnormal situations. Such networks are able to support a diverse range of applications with traffic rates ranging from several bits per hour up to 10 megabits per second. For the efficient functionality of these applications, each one poses a specific set of quality of service (QoS) requirements to the medium access control (MAC) sub-layer including transmission reliability, timeliness, and throughput. However, energy limitations of WBANs make the satisfaction of these requirements a challenging task. The current paper aims to explore the application trends of WBANs in the health field as well as the salient features of the MAC protocols proposed for this class of networks and to provide a general rule indicating the most suitable MAC technology for WBANs based on the characteristics of the targeted application.