Under Weighing. This Method (called densimetric) is based on the fact that fat tissue is lighter than other body tissue-bones, muscle, blood, and water. The person is weighed while submerged underwater, with as much air as possible exhaled from the lungs. he or she is then weighed normally on the ground. By using a formula based on the two weights, the percentage of body fat can be determined.
Skin fold thickness. About 50 percent of back fat situated just below the skin, and by measuring folds of skin on certain part of the body, the percentage of body can be estimated. The most accurate measurement are obtained by using calipers; indicative body sites include the triceps (the skinfold on the back of the arm midway between the shoulder and elbow), the sub scapular area below the shoulders blades, and the area justa above the hip bone.
Total body water (hydrometry). Most fat free tissue (muscle) contains water, while fat tissue has very little. Therefore, measurement of total body water provides an estimate of Fat Free Mass (FFM). One approach to this measurement is taken by injecting a known amount of a substance that distributes itself throughout the body’s water compartments. A blood sample, taken after enough time elapsed for the substance to reach a stable concentration in the body, reveals the substance’s distribution in body water, allowing the tester to measure total body water and from that to calculate the amount of FFM. The result obtained by subtracting FFM from total body weight is the body fat content. Another approach is by putting two electrodes on a limb and measuring resistance to an electric current. The amount of electric impedence measures body water.
Whole body potassium. Almost all of the body’s potassium is contained in cells other than adipose tissue. A naturally occurring isotope of potassium exists as a fixed proportion to all potassium found in the body. The radioactive portion can be measured by counting the gamma rays it emits, and this can be used to estimate the total potassium. The greater the amount of potassium in relation to body size, the smaller the percentage of body fat.
Skin fold thickness. About 50 percent of back fat situated just below the skin, and by measuring folds of skin on certain part of the body, the percentage of body can be estimated. The most accurate measurement are obtained by using calipers; indicative body sites include the triceps (the skinfold on the back of the arm midway between the shoulder and elbow), the sub scapular area below the shoulders blades, and the area justa above the hip bone.
Total body water (hydrometry). Most fat free tissue (muscle) contains water, while fat tissue has very little. Therefore, measurement of total body water provides an estimate of Fat Free Mass (FFM). One approach to this measurement is taken by injecting a known amount of a substance that distributes itself throughout the body’s water compartments. A blood sample, taken after enough time elapsed for the substance to reach a stable concentration in the body, reveals the substance’s distribution in body water, allowing the tester to measure total body water and from that to calculate the amount of FFM. The result obtained by subtracting FFM from total body weight is the body fat content. Another approach is by putting two electrodes on a limb and measuring resistance to an electric current. The amount of electric impedence measures body water.
Whole body potassium. Almost all of the body’s potassium is contained in cells other than adipose tissue. A naturally occurring isotope of potassium exists as a fixed proportion to all potassium found in the body. The radioactive portion can be measured by counting the gamma rays it emits, and this can be used to estimate the total potassium. The greater the amount of potassium in relation to body size, the smaller the percentage of body fat.
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