In this paper, power and rate are allocated to each eigenchannel of the multiple-input-multiple-output (MIMO) on-body channel under average transmit power and bit error rate (BER) constraints. Three on-body channels, i.e., the belt-head, belt-wrist, and belt-chest channels, are of interest when adopting either discrete- or continuous-rate schemes. First, the on-body channel is modeled using the joint correlation matrix by taking into account the different propagation mechanisms experienced by the spatial subchannels, then the performance in terms of the spectral efficiency of the simulated channel using the model is shown to be in good agreement with the measurements. Owing to the presence of a line-of-sight (LOS) component, the achievable spectral efficiency of the on-body channels is lower than that of the equivalent Rayleigh channel. Due to its low spatial subchannel correlation, the belt-head channel is shown to offer the best performance in terms of spectral efficiency.