Wireless Body Area Sensor Networks (WBASNs) have emerged as a promising solution for continuous health monitoring and medical diagnostics. However, the sustainability of this network is often limited by the finite battery life of the wearable sensors. To address this issue, an energy harvesting techniques are being explored to extend the operational lifetime of WBAN. This paper proposes a comprehensive review on various recent energy harvesting methods including solar, thermal, kinetic, and radio frequency (RF) energy harvesting, and their applicability in WBANs that include security, privacy, and QoS etc. Further, the advantages and limitations of recent algorithms of energy harvesting techniques are being discussed, and also focus on energy efficiency, integration with small-scale wearable sensors, and environmental compatibility. Our findings show that each method offers significant potential for power supply augmentation, challenges related to low energy conversion efficiency and the variability of ambient energy sources remain. Here, we concluded a hybrid energy harvesting system as a promising solution to enhance energy sustainability in WBASNs. This review can play a vital role in finding the solution for enabling long-term, real-time monitoring in healthcare and other critical applications, while reducing the dependence on battery replacements is prime concern.