Power efficiency and spectral efficiency are crucial considerations in the realm of Wireless Body Area Networks (WBANs). Therefore, the objective of this study is to design a secure, spectral-efficient, and power-efficient system suitable for on-body deployment. To achieve this goal, we propose a millimeter wave (mmWave) massive Multiple-Input-Multiple-Output (MIMO) system with a hybrid analog/digital transceiver architecture. In our approach, we employ Orthogonal Frequency Division Multiplexing in a mmWave MIMO system, utilizing the Barzilai-Borwein Gradient algorithm. This algorithm serves as the basis for optimizing the performance of our system model. To evaluate the effectiveness of our approach, we compare the results of both spectral efficiency and power efficiency with those obtained from alternative minimization algorithms. The simulation results demonstrate the effectiveness of all algorithms in improving spectral and power efficiency. Specifically, we observe that the optimal digital precoder surpasses the hybrid precoder in terms of spectral efficiency. However, the hybrid precoder exhibits a significant improvement in energy efficiency performance. These findings highlight the trade-off between spectral efficiency and power efficiency in our proposed system. The optimal digital precoder excels in achieving higher spectral efficiency, while the hybrid precoder greatly enhances energy efficiency performance. Overall, our study presents a promising solution for achieving a secure, spectral-efficient, and power-efficient device for deployment in WBANs.