Method and apparatus for measuring body fat

#The present invention relates to an improved method and apparatus for measuring the body fat of a live subject, and more particularly, of a living human being.

#Body composition, and in particular percent body fat, is a well-recognized measure of physical health. Various techniques of determining percent body fat are presently in use, including caliper measurements, underwater displacement measurement, and bioelectrical impedance measurement.

#In this last technique, as described in U.S. Pat. Nos. 5,415,176 and 5,611,351, both to Sato et al., a live subject whose body fat is to be measured stands upon a scale-like device with four electrodes mounted on its upper surface. A 50 kHz, 800 microampere electric current is produced by constant current source. This current is passed first through two electrodes in contact with the subject's toes and then through two reference resistors located in series with the subject's body and with each other. The electric current flowing through the subject causes a voltage potential to develop across the subject's heels.

#FIG. 1 is a block diagram illustrating a body fat analyzer embodying present invention.

#FIG. 2A illustrates a top-view of an electrode array mounted upon the upper surface of a body fat analyzer embodying the present invention.

#FIG. 2B illustrates a cross-sectional view of the device shown in FIG. 2A.

#A device embodying the present invention, as shown in a preferred embodiment in FIG. 1., comprises a 50 kHz, 300 microampere constant current source 10 connected in parallel with a plurality of reference resistors Ri (R1, R2, and R3 being shown as examples in FIG. 1) and with the subject's body 60. Resistors Ri and the subject's body 60 are switched in and out of the circuit by switches Sj (S1 through S8 in the embodiment shown in FIG. 1), which are controlled by microprocessor control unit (“MCU”) 120. In the embodiment shown in FIG. 1, the various voltages across the resistors and the body are connected sequentially to voltage drop measuring device 70 via switches S9 through S12, also controlled by MCU 120.

#For example, to measure the voltage developed across body 60, switches S7, S8, S11, and S12 are closed, while switches Si through S6, S9 and S10 are opened. Thus, current flows through the current-supply electrode group 20, which is in contact with one of the subject's heels, through body 60 and through the current-supply electrode group 30 in contact with the subject's other heel. Simultaneously, the voltage generated between the balls of the subject's feet is passed through voltage-detecting electrode groups 40 and 50, which are in contact with the balls of the subject's feet, to the inputs of voltage drop measuring device 70. Similarly, to measure the voltage developed across resistor R1, switches S1, S2, S9, and S10 are closed, while switches S3 through S8, S11, and S12 are opened. In this way, the voltage across any of the resistors or the subject's body may be measured.

#Additionally, combinations of the references resistors Ri (R1, R2, and R3 in FIG. 1) and body 60 can be connected and the voltage across the combination measured. For example, resistors R1 and R2 can be connected by closing switches S1, S2, S3, S4, S9, and S10, and opening the other switches. Thus, a large number of resistance/voltage data points with a narrow resolution of resistance values can be obtained. Furthermore, the number of potential data points can readily be increased by increasing the number of reference resistors Ri in parallel with body 60. The resolution of the data points is set by the values of the reference resistors and the equivalent resistances of groups of resistors; the reference resistors are selected such that the full range of body impedance, which is typically 0 to 1000 ohms, is bracketed.