Results of recent investigations into frequency dependence of the path loss for ultra wideband implant body area networks are presented. Contributions of this paper are threefold. First, explicit mathematical expressions, which highlight the highly nonlinear relationship between frequency and path loss are presented. These mathematical relationships should be of interest to system designers designing implant communication systems in the UWB regime. Secondly, frequency dependence of the scattering component of the path loss is investigated and discussed. Thirdly, the proposed model is used to identify sub-bands within the UWB band that minimise amplitude distortion at the receiver side. (C) 2015 Elsevier Ltd. All rights reserved.