( Originally Published 1956 )
DIAGNOSIS of caloric undernutrition or over-nutrition is relatively easy if deviation from the normal is great but minor deviations cannot be determined with precision. The dietary history is of some assistance in estimating the extent of caloric deficit or surplus in spite of the difficulties in ascertaining daily food consumption accurately. Knowledge of energy requirements according to age, sex, body size and physical activity is necessary for interpretation of findings. Approximate caloric needs of populations groups, and to a lesser extent of individuals, may be determined with the use of schedules prepared by several national and international groups. The requirement for an individual may be obtained more accurately by calculating his basal metabolic needs and adding the amount required for physical activity. The importance of calories during growth was emphasized by Macy and Hunscher (13) who pointed out that as few as 10 calories per kilogram of body weight per day may may make the difference between progress and failure.
In evaluating height and weight in children, growth charts may be used but interpretation should be cautious. Ideal weight for height is not known for either children or adults. In adults, desirable weight may be considered to be the average weight, for a given height and type of body build, of persons 25 years of age who are in good health. More precise definition of ideal weight must await further knowledge. The height-weight standards used currently represent arithmetic averages of findings in selected population groups. In most instances, data were obtained at the time of application for insurance, the individuals being weighed and measured in ordinary clothes
The inexactness of such standards is apparent. Clothing and height of heels introduce appreciable variables.
In some standards, average weights are given for light, medium and heavy body types. No accurate method of determining body build is available although a rough appraisal can be made by the experienced clinician. Measurement of bi-cristal (bi-iliac) diameter is of assistance
Determination of bi-acromial diameter is also useful but is more difficult to obtain accurately, due to the influence of posture on this measurement.
Genetic variations and environmental factors, such as climate, should be taken into account in height-weight appraisal. Available standards are useful if interpretations are made with appreciation of their inexactness. An individual who is less than "standard" weight may be lean, or have poorly developed muscles or a small skeleton. An individual whose weight exceeds the standard may be excessively fat, or may have a large muscle mass or a large skeleton.
It would be desirable to estimate the relative proportion of the components of the total body mass, namely, bones, muscles, extracellular fluid and adipose tissues. Recently, biophysical and biochemical methods have been devised for estimation of body composition and have been applied in evaluation of leanness and fatness in man. Total body fat may be estimated by determining the specific gravity of the body, by estimating total body water, and by measurement of the thickness of subcutaneous tissues,muscle and bone in x-ray photographs. Mc-Cance, Williamson and associates calculated body fat either from total body water, or by subtracting the weight of the extracellular fluid, cell mass and minerals in the skeleton, from the total body weight. Minerals were estimated as 7% of the fat free body. The weight of cellular tissues was determined by assuming that cells contain 67% water and estimating intracellular water as the difference between total body water and extracellular space. Keys and associates suggested estimation of cell or "active' tissue mass as body weight less fat, extracellular fluid and bone mineral, fat being determined from body density. These methods are of importance in research and may be used as criteria for evaluating simpler procedures which the clinician can apply.
An indirect method for estimation of fatness or leanness which seems promising is measurement of the thickness of skin folds in several areas of the body with specially constructed calipers. Good correlation has been demonstrated in adult males between findings with this method and determination of specific gravity of the body (16, 17). Correlation has also been demonstrated between pinch-caliper and x-ray measurements of the thickness of skin and subcutaneous fat. The use of skinfold measurements as criteria for evaluating fatness or leanness of the body requires further study. Data available at present suggest that measurements of skin fold thickness at two sites are of value: the back of the right upper arm and below the tip of the right scapula. Details of the procedure are given in a recent publication in which other anthropometric measurements for characterization of nutritional status are also discussed (15). Skinfold measurements in a large group of young American males, white and negro, are included in this report.
Muscular development of an individual can be estimated by determining the breadth of the muscular segments of soft tissue x-rays of the extremities. Some information can be obtained by measurement of limb circumference if thickness of the skin and subcutaneous fat is determined at the same time.
With application and improvement of the methods indicated above, diagnosis of caloric nutriture should be-come more exact. It is anticipated that more adequate "norms" as "standards" will be developed for population groups of varying genetic potentialities and environmental situations.
The serious medical hazard of obesity is attested by insurance data which indicate that if the death rate of the standard risk is taken as 100, the mortality of men who are moderately overweight is 142 and of those markedly overweight 179. The respective values for women are 142 and 161. Overweight as judged by standard height-weight-age tables does not necessarily mean obesity which should be defined as a disproportionately large fat content of the body. The incidence of diseases of the heart, arteries and kidneys, of diabetes mellitus, of gallbladder disease, and even of neoplasia is increased in persons who are overweight (21). Important information might be obtained by application of the newer methods of estimating body composition in examination of overweight persons in whom various pathologic conditions have developed. The recent implication of lipids in the pathogenesis of atherosclerosis has stimulated interest in this field. Much remains to be learned about the role of excessive fat accumulation and of lipid metabolism in the pathogenesis of disease. However, sufficient information is at hand to indicate the desirability of maintaining normal body weight and avoiding excessive fatness.