A method and system for estimating fractional fat content of an object of interest. An energy emitter is used to direct an energy signal toward the region of interest, wherein the region of interest has an object of interest, a reference, and a boundary area with one or more boundary locations between the object of interest and the reference. Next, a plurality of thermoacoustic or ultrasonic transducers is used to receive a plurality of thermoacoustic bipolar signals from the one or more boundary locations, wherein the thermoacoustic bipolar signals are induced by the energy signal. A machine configured to accept data from the energy emitter and the plurality of thermoacoustic or ultrasonic transducers and calculate a fat concentration that is a function of the thermoacoustic bipolar signal at each respective boundary location and the distance or distances between locations.