Body-coupled communication (BCC) is a promising technology that enables wireless communication around and limited to the human body. It consists in generating low-power electric fields at the surface of the human body for transmitting signals. Its physical (PHY) layer has several advantages over classical radio frequency (RF) PHY layers, e.g., IEEE 802.15.4, for body-area networks (BANs), like a better robustness to body shadowing and a greater energy efficiency. From the medium access control (MAC) point of view, BCC BAN networks are a sub-class of wireless sensor networks (WSNs). Because WSN nodes are battery-powered device with limited energy capacity, energy efficiency is a key requirement for many applications. A low power MAC protocol is one of the component that enables to fulfill such a requirement. However current solutions developed so far by the scientific community are solely targeting RF systems. The properties of the BCC PHY layer are such that using those solutions would lead to inefficient energy usage. Therefore we developed and present in this paper AdaMAC a new MAC protocol that takes into account the specific properties of the BCC PHY layer. Compared to state-of-the-art protocols AdaMAC performs better in terms of reliability, latency and energy efficiency when applied to BCC systems.