Assessment of body composition by bioelectrical impedance in a population aged > 60 y

Article Abstract:

In recent years, interest in the nutrition and health of the elderly has increased because the population as a whole is aging. One measure of nutritional health is body composition, an index of the relative proportions of fat and lean tissues in an individual. Body composition is known to shift with aging towards greater amounts of body fat and less lean tissue, or fat-free mass (FFM), which include muscle, bone and body water. A new technique for body composition analysis, bioelectrical impedance (BIA), is quick, accurate, and can easily be used for persons confined to bed. Electrodes are attached to the wrist and foot and a painless electrical current is passed through the body. The speed at which the current travels indicates how much fat is in the body, since electricity is conducted more efficiently through FFM than fat. While many studies have now established the reliability of BIA in younger populations, its accuracy has not been tested in the elderly. Seventy-two men and women aged 60 to 83 were assessed by BIA and other methods of body composition analysis. The average percent body fat was 31.0 for men and 43.9 for women. BIA was found to be a reliable method for estimating body fat and FFM in these elderly subjects. Equations were devised for calculation of FFM in the elderly; similar equations taken from the literature on younger subjects were not accurate for older persons and should not be used for them, as they tended to underestimate body fat in the elderly. (Consumer Summary produced by Reliance Medical Information, Inc.)

Aged, Elderly, Food and nutrition

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The menstrual cycle's effect on the reliability of bioimpedance measurements for assessing body composition

Article Abstract:

Bioimpedance is a relatively new method for evaluating body composition. Electrodes are attached to the patient's hand and foot, and a painless electrical current is sent through the body. Electricity travels at a different rate through fat tissue versus fat-free tissue (body water, bones). The resistance that the current encounters while traveling through the body indicates the approximate proportions of fat and lean tissue; calculations yield percent body fat. This method of estimating body composition has several advantages over other approaches. Bioimpedance is quick, noninvasive, inexpensive, and the equipment is easily transported. Some investigators have found its accuracy to be high when compared to other, more established techniques. But various sources of error in the bioimpedance technique have not yet been evaluated. In women, the stage of the menstrual cycle may affect bioimpedance readings because of cyclical changes in body temperature, diet, and fluid and sodium retention. Twenty-five healthy women aged 20 to 41 participated in a study in which their dietary sodium intake was assessed, and weight and bioimpedance readings were taken during four parts of the menstrual cycle. Results showed that variation in readings attributed to changing hydration status were minor, and that bioimpedance appeared sufficiently reliable for general use in community settings. Women who experience large premenstrual weight gains (more than 0.7 pounds) should have several bioimpedance readings taken throughout the month and use the average.

Analysis, Physiological aspects, Impedance, Bioelectric, Bioelectric impedance, Menstrual cycle

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Body composition in children: proposal for a method for calculating body fat percentage from total body density or skinfold-thickness measurements

Article Abstract:

An accepted conceptual approach for studying body composition is to divide the body into two components, fat and fat-free mass. The fat-free tissues include bones, water and muscles. There are several methods for evaluating body composition and thereby estimating percent body fat to diagnose obesity, but all methods have drawbacks, particularly for use with children. A reliable method for evaluating body composition and diagnosing obesity in children is needed. An approach is described that allows estimation of percent body fat from measurements of skinfolds. To obtain skinfold measurements, a caliper is used to pinch the fat under the skin at various locations on the body. Using the reference tables presented, the sum of four skinfold measurements from an individual child can be translated into percent body fat. General guidelines for diagnosis of obesity using percent body fat are given; for example, values for percent body fat greater than 30 percent are considered indicative of obesity in children before the age of puberty.

Diagnosis, Obesity in children, Childhood obesity

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