This paper presents a new method of adapting body biasing on a chip during post-fabrication testing in order to mitigate the effects of process variations. Individual well biasing voltages can be changed to be connected either to a chip wide well bias or to a different bias voltage through a self-regulating mechanism, allowing biasing voltage adjustments on a per well basis. The scheme requires only one bias voltage distribution network, but allows for back biasing adjustments to more effectively mitigate die-to-die and within-die process variations. The biasing setting for each well is determined using a modified genetic algorithm. Our experimental results show that binning yields as low as 17% can be improved to greater than 90% after using the proposed IWABB method.