Method and apparatus for measuring body fat

• US 6,473,643 B2
• Filed: 10/01/2001
• Issued: 10/29/2002
• Est. Priority Date: 09/30/2000
• Status: Expired due to Term

• Current Assignee: Fook Tin Plastic Factory, Ltd.
• Original Assignee: Fook Tin Plastic Factory, Ltd.
• Inventors: Chai, Sunny, Cha, Frederick C.
• Primary Examiner(s): Hindenburg, Max
• Application Number:
  US09/968,727
• Publication Number:
  US 20020062090A1
• Time in Patent Office: 393 Days
• Field of Search: 600/546, 600/547, 600/587
• US Class Current: 600/547
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/4872 Body fat
• CPC Class Codes: A61B 5/6829 Foot or ankle

Abstract

An improved apparatus and method are provided for measuring body fat of a live subject. The apparatus comprises a current source connected in parallel with two or more reference resistors and with the subject'"'"'s body. The connections to the body are made via an array of electrodes. The resistors and the subject'"'"'s body are switched in and out of the circuit, and the various voltages across the resistors and the body are detected by a voltage drop measuring device and input to an analog-to-digital convertor (ADC). The output from the ADC is presented to a microprocessor control unit, which calculates (1) the impedance of the individual'"'"'s body based upon the various voltage measurements, and (2) the percent body fat as a function of that impedance and other ariables such as height, weight, age, and sex.

Claims

1. A device for measuring the percent body fat of a subject'"'"'s body, comprising:

a. a housing;

b. an array of five or more electrodes, mounted on said housing and arranged to contact such body,

c. a current source connected to at least two electrodes in said array, whereby current may be supplied to such body, causing a voltage to develop across the body;

d. a voltage amplifier connected to at least two electrodes in said array, whereby the voltage across said electrodes may be received and amplified; and

e. a microprocessor, connected to said amplifier, and configured to compute the subject'"'"'s percent body fat based on the amplified voltage;

whereby said electrodes contact such body at discrete points, allowing largely-unrestricted blood flow at the surface of such body near said electrodes and thereby improving the reliability of the measurement.

2. The device of claim 1, wherein at least two of the electrodes in said array of five or more electrodes are electrically connected together.

3. The device of claim 1, wherein said array of electrodes includes:

a. a first array of current-supply electrodes connected to said current source; and

b. an second array of voltage-detecting electrodes connected to said voltage amplifier.

4. The device of claim 3, wherein the electrodes to which said current source is connected are in said first array, and wherein the electrodes to which said voltage amplifier is connected to are in said second array.

5. The device of claim 3, wherein each of the electrodes of said first array is mounted at least about one centimeter away from each of the electrodes in said second array.

6. The device of claim 3, wherein at least five of the five or more electrodes in said array serve as at least one of a current-supply electrode and a voltage-detecting electrode.

7. The device of claim 3, wherein

a. the electrodes in said first array are grouped to form a first and a second group, and all of the electrodes in each group are electrically connected together, and each group is connected to said current source;

and

b. the electrodes in said second array are grouped into a third and a fourth group, all of the electrodes each group are electrically connected together, and each group is connected to said voltage amplifier.

8. The device of claim 7, wherein said housing has four quadrants, and each group of electrodes is mounted in one of said quadrants.

9. The device of claim 8, wherein said groups are arranged on said housing such that when such subject stands on said housing,

a. said first and second groups contact the heels of his feet and

b. said third and fourth groups contact the balls of his feet, whereby measurement errors caused by variations in heel-toe impedance are avoided.

10. The device of claim 1, wherein when such subject is in contact with said electrodes, an electrical current not greater in magnitude than about 300 microamperes flows through the subject'"'"'s body.

11. The device of claim 10, wherein said current is about 300 microamperes.

12. The device of claim 1, wherein the surface of said housing is substantially rigid.

13. The device of claim 12, wherein the surface of said housing is glass.

18. The method of claim 1, wherein at least two of the electrodes in said array of five or more electrodes are electrically connected together.

14. A device for measuring the percent body fat of a subject'"'"'s body, comprising:

a. two or more voltage-detecting electrodes capable of contacting an extremity of such body;

b. two or more current-supply electrodes capable of contacting such extremity at a location that is proximally closer to such body than that of the two or more voltage-detecting electrodes;

c. a current source connected to said current-supply electrodes, whereby current may be supplied to such body;

d. a voltage amplifier connected to said voltage-detecting electrodes, whereby a voltage across said such body may be received and amplified; and

e. a microprocessor, configured to compute percent body fat based on the voltage detected by said voltage-detecting electrodes;

whereby measurement errors caused by variations in the impedance of the extremity are reduced.

15. The device of claim 14, wherein

a. said current-supply electrodes contact the heels of such subject'"'"'s feet; and

b. said voltage-detecting electrodes contact the balls of such subject'"'"'s feet.

16. A device for measuring the percent body fat of a subject'"'"'s body, comprising:

a. two or more electrodes capable of contacting such body;

b. two or more reference resistors arranged in parallel with such body;

c. a current source;

d. a voltage amplifier;

e. a controllable switch, capable of connecting said current source and said voltage amplifier to said electrodes and to said reference resistors, such that current may be supplied to such body and said resistors and a voltage across them may be received and amplified; and

f. a microprocessor, connected to said amplifier, and configured to compute the subject'"'"'s percent body fat based on the amplified voltages;

whereby the device remains operational even if the connection to one of said reference resistors fails.

17. A method of measuring the percent body fat of a subject'"'"'s body, comprising the steps of:

a. sourcing current to at least two electrodes in an array of five or more electrodes contacting such body;

b. receiving and amplifying a voltage across at least two electrodes in the array of electrodes; and

c. calculating the subject'"'"'s percent body fat based on the amplified voltage;

whereby the five or more electrodes contact such body at discrete points, allowing largely-unrestricted blood flow at the surface of such body near said electrodes and thereby improving the reliability of the measurement.

19. A method of measuring the percent body fat of a subject'"'"'s body, comprising the steps of:

a. sourcing a current through two or more current-supply electrodes contacting an extremity of such body;

b. receiving and amplifying a voltage at two or more electrodes contacting such extremity at a location that is proximally more distant from the core of the body than that of the two or more current-supply electrodes; and

c. calculating the subject'"'"'s percent body fat based on the amplified voltage;

whereby measurement errors caused by variations in the impedance of the extremity are reduced.

20. A method of measuring the percent body fat of a subject'"'"'s body, comprising the steps of:

a. sourcing a current through two or more reference resistors arranged in parallel with the body;

b. receiving and amplifying a voltage developed across one or more of the reference resistors;

c. sourcing a current through two or more electrodes contacting the body;

d. receiving and amplifying a voltage at two or more electrodes contacting the body;

e. calculating the subject'"'"'s percent body fat based on the received and amplified voltage;

whereby the device remains operational even if the connection to one of the reference resistors fails.