Noticeable performance degradation of IEEE 802.15.4-based wireless body sensor networks (WBSNs) caused by the mutual interference has recently drawn the attention of research communities. Frequency-adaptation is to some extent an effective solution to reduce the impact of mutual interference on WBSN's performance. However, as the number of WBSNs becomes larger, this scheme is destined to fail. In this paper, a new scheme called “dynamic-phase-shifting” is proposed in which a WBSN is able to shift its beacon packets to other phases (time slot) in order to finally settle down in a phase with reasonably higher performance gain. A set of performance measures is used to provide performance comparison between the dynamic-phase-shifting scheme and a baseline scheme (that follows IEEE 802.15.4 standard). The results indicate that the dynamic-phase-shifting scheme is not only feasible to be implemented on real sensor devices but also it outperforms IEEE 802.15.4 standard in terms of the considered performance measures.