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close this bookChronic Energy Deficiency : Consequences and Related Issues (International Dietary Energy Consultative Group - IDECG, 1987, 201 pages)
close this folderEffects of chronic energy deficiency on stature, work capacity and productivity
View the document(introductory text...)
Open this folder and view contents1. Studies in adults
Open this folder and view contents2. Studies in children
Open this folder and view contents3. Men and boys
View the document4. Productivity, earning and nutrition in developing countries
View the document5. Summary
View the documentAcknowledgements
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(introductory text...)

G.B. SPURR*

* Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road Milwaukee, WI 53226, U.S.A.

In general, there is an association between economic development and adult body size. The small adult stature of people in developing countries is a common feature of many nutritional surveys (Interdepartmental Committee on Nutrition for National Defense, 1959-63). In Figure 1, the adult height in several Latin American nations is compared with that of adults in the United States (SPURR, BARAC-NIETO and MAKSUD, 1978). The division of the Colombian data into upper and lower socioeconomic groups demonstrates that the ethnic component contributes little to the observed differences, as has been emphasized by HABICHT et al. (1974). MARTORELL (1985) has pointed out that the cause of the small stature of adults in developing countries, where nutritional deficiencies are prevalent (BERG, 1973; 1981), is the result of chronic undernutrition and infection during the period of growth. In general, differences are related to socioeconomic level with manual workers being shorter than non-manual workers and university students being the tallest in all countries (EVELETH, 1985).

The present paper will discuss the effects of chronic energy deficiency and associated small body size on physical work capacity (PWC) and productivity in heavy physical work. The concern with PWC and its relation to hard physical work is valid only if both hard physical work and malnutrition are associated. In the less developed areas of the world, where the incidence of protein-calorie undernutrition is high and mechanization is at a minimum, human labor provides much of the power for economic productivity (SMIL, 1979). Using data published by the United Nations (e.g., United Nations Demographic Year Book, 1979), it is possible to estimate for six South American countries that about 54% of the actively employed male population is engaged in work which can be classified as moderate to heavy (agriculture, forestry, mining, construction, etc.). ARTEAGA (1976), using the same source of data for 1972, concluded that in all of Latin America, about 54% of employed men were engaged in heavy work, 20% in medium intensity work and 26% in sedentary occupations. The data in Table 1 extend these observations. Consequently, hard physical work is a reality for the majority of adult males in the work force of poor countries, and factors which affect it will have a bearing on economic development (MARTORELL, 1 985).

In what follows, our own studies in adults and those of others which relate physical work capacity, as measured by the maximum oxygen consumption (VO2 max), to productivity and nutritional status will be presented. The data show a strong relationship between body size and VO2 max. The physiological relationship between body size and VO2 max. on the one hand, and productivity in hard physical work on the other, is an indirect one, but nevertheless real.

MARGEN (1984) has stated that, while it is obvious that a larger individual can perform heavier work than a small one, this may not be the proper interpretation since, if expressed per unit of lean body mass (LBM), the work which can be performed by a small person is as great as that of a large one. Others have also suggested that because the rate of energy expenditure is proportional to body size (weight), smaller individuals will be disadvantaged in hard work only when VO2 max per kg of body weight is also reduced (FERRO-LUZZI, 1985; WATERLOW, 1986). This presentation will attempt to show that mild to moderate malnutrition is accompanied by functional decrements in work capacity which have particular importance when it occurs during the period of growth, and that it is the total work capacity which matters, not the physical work capacity normalized for weight or LBM.


Figure 1. Average heights of adult men and women from several Latin American countries and the United States (SPURR et al., 1978).

Table 1. Percentage of economically active populations engaged in moderate to heavy physical work (agriculture, hunting, fishing, forestry, mining and construction) of some countries (United Nations, New York, 1980).

Country

Male

Female

Honduras

75.1

7.5

Ecuador

58.7

13.0

Guatemala

70.5

7.1

Brazil.

9

20.7

Costa Rica

52.7

4.3

Venezuela

33.9

3.6

Sri Lanka

50.8

62.1

Philippines

72.0

35.8

Cameroon

67.6

87.4