This book constitutes the refereed post-conference proceedings of the 16th International Conference on Body Area Networks, BodyNets 2021, held in October 2021. The conference was held virtually due to the COVID-19 pandemic. The 21 papers presented were selected from 44 submissions and issue new technologies to provide trustable measuring and communications mechanisms from the data source to medical health databases. Wireless body area networks (WBAN) are one major element in this process. Not only on-body devices but also technologies providing information from inside a body are in the focus of this conference. Dependable communications combined with accurate localization and behavior analysis will benefit WBAN technology and make the healthcare processes more effective.