With the growth of the demand of smaller and smaller implantable devices, THz technologies becomes appealing for potential applications in Body Area Networks at nano-scale. As an essential part for understanding the in-body propagation at THz frequency numerical investigations are presented in this paper to simulate the absorption path loss of fat at THz frequency. The results of the proposed analysis suggest that a distance in the order of millimeter might be suitable to guarantee a communication link between nanodevices located in human tissues.