Parameter variation is detrimental to a processor's frequency and leakage power. One proposed technique to mitigate it is Fine-Grain Body Biasing (FGBB), where different parts of the processor chip are given a voltage bias that changes the speed and leakage properties of their transistors. This technique has been proposed for static application, with the bias voltages being programmed at manufacturing time for worst-case conditions. In this paper, we introduce Dynamic FGBB (D-FGBB), which allows the continuous re-evaluation of the bias voltages to adapt to dynamic conditions. Our results show that D-FGBB is very versatile and effective. Specifically, with the processor working in normal mode at fixed frequency, D-FGBB reduces the leakage power of the chip by an average of 28-42% compared to static FGBB. Alternatively, with the processor working in a high-performance mode, D-FGBB increases the processor frequency by an average of 7-9% compared to static FGBB - or 7-16% compared to no body biasing. Finally, we also show that D-FGBB can be synergistically combined with Dynamic Voltage and Frequency Scaling (DVFS), creating an effective means to manage power.