Fat-free mass in children and young adults predicted from bioelectric impedance and anthropometric variables

Article Abstract:

Fat-free mass is the proportion of the body that contains no fat tissue. Some components of fat-free mass are bone, muscle, and body water. Researchers and clinicians are interested in estimating fat-free mass in the human body because it influences daily caloric needs, athletic performance and the action of drugs in the body. For example, the greater the individual's fat-free mass, the higher the caloric needs (per pound of body weight). This is because lean tissue, such as muscle, requires more energy to function than fat (adipose) tissue. The metabolism of muscle is faster than the metabolism of fat, although both require energy to exist. While fat-free mass cannot be directly measured in a living person, it can be estimated. The authors developed a multicomponent model, which uses multiple pieces of information in an equation, to estimate fat-free mass in children and young adults. Their model is based on an assumption that fat-free mass varies in its composition with both age and sex. The variables that most accurately predicted fat-free mass when put together in an equation were body weight, arm muscle circumference, skinfold measurements (indicators of body fat), and the result of bioelectrical impedance. Bioelectrical impedance is a test that estimates body fat by sending an electrical current through the body. In this painless procedure, the current travels faster in people who have more water (and less fat) because water is an electrical conductor. The multicomponent model was found to be more accurate than a two-component model in a comparison using 465 men and 441 women. This multicomponent model may be used to predict fat-free mass of healthy white persons, 7- to 25-years-old.

Models, Usage, Fat, Fats, Densitometry

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Status of anthropometry and body composition data in elderly subjects

Article Abstract:

Body composition refers to the proportions of various tissues in the body; these include fat, muscle, body water, and bone. Throughout life, body composition changes. From young adulthood to old age there is a gradual increase in body fat and a decrease in lean tissues such as muscle and bone. While this general trend has been established, normal standards for body composition at various ages and for different ethnic groups have not been determined. There are some data on white persons between 65 and 80, but virtually no research on those over 80, or elderly black, Oriental and Hispanic individuals. The fastest growing segment of the United States population is that over age 85, and this group is also experiencing the most rapid rise in medical expenditures. Reference data on body composition in the elderly are needed so that the normal patterns are known; on this basis individuals with measurements that indicate health risks can be identified and treated. Knowledge of an individual's body composition can improve his medical care, particularly in planning appropriate nutritional support (feeding by intravenous or stomach tube) and selecting proper medication dosages. Techniques for estimating body composition in elderly persons, particularly those who are confined to a bed or chair, are discussed. Some methods appear promising but have not yet been validated for use with the elderly by comparing them against accepted techniques.

Aging, Aged, Elderly, Standards, Physiological aspects, Food and nutrition, Obesity, Leanness

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Estimation of body composition from bioelectric impedance of body segments

Article Abstract:

Estimating the composition of body mass from indirect and simple measurement techniques can prove useful for making such assessments when the current procedures would be stressful or made impossible by the patient's other needs. For instance, measurement of the body's lean mass is achieved by submerging a person in water and weighing him. This obviously would be inappropriate and potentially damaging to many debilitated patients. The current paper proposes a model system that provides data of sufficient accuracy for measurements of weight by measuring the length and electrical resistance of the arm. The electrical calculations are made by applying two electrodes to the arm and measuring the flow of a harmless electrical current between them with a standard reference voltage (AC). These data differ only slightly from similar measurements obtained by using the electrical impedance of the trunk. Although this method appears to be useful for estimating body composition from simple measurements which can be obtained at bedside, care should be exercised until cross-validation of the mathematical formulas can be obtained.

Research, Muscles, Impedance, Bioelectric, Bioelectric impedance

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