Rural-to-urban migration in Latin America: an update and thoughts on the model.

Urbanization is an important demographic phenomenon, and in Latin America it transformed the settlement pattern from rural to predominantly urban in less than 50 years. Understanding the biological consequences of this change in settlement pattern is an important challenge for human biologists. One approach to understanding the effects of urban environments on human biology has been to study rural-to-urban migrants. In Latin America this research has shown that 1) the fertility of migrants tends to be intermediate between that of rural and urban populations, and 2) migrants tend to suffer higher rates of mortality and morbidity, at least initially, than long-term urban residents. There is some indication that the actual physical conditions under which migrants live in urban areas-and these tend to be among the most impoverished-are more important variables than migrant status per se. Studying rural-to-urban migrants requires careful attention to a number of conceptual issues. One issue is the definition of rural and urban. These two types of settlements are no longer as distinct as they once were, and "urban" can mean very different things in different places. Another issue is the complexity of current migration patterns. The classic case of people moving from a distinctly rural setting to a distinctly urban one and staying there for the remainder of their lives is not the norm. Third, the urban environments of large cities are extraordinarily heterogeneous environments with enormous socioeconomic differentials in health. Hence, it matters where in the urban environment the migrants live.

Physical activity of poor urban women in Cali, Colombia: a comparison of working and not working women.

We have previously presented evidence that the physical activity level (PAL) and total energy expenditure (per kg body weight) of poor urban women who "work" (engage in income-earning activities) is similar to those who do not "work" (but do tend to household and childcare responsibilities) (Spurr et al. [1996] Am J Clin Nutr 63:870-878; [1997] Med Sci Sports Exerc 29:1255-1262). These findings were unexpected and raised questions regarding the actual types of activities engaged in by the two groups. In this article we address those questions by comparing the time allocation of the two groups. Time allocation during waking hours (14.2 +/- 1.1 hours/day) was recorded in minute-by-minute diaries by trained observers for two consecutive days for 52 working women and 28 not-working women. The working women were engaged in predominately informal sector economic activities, such as street vending, childcare, and domestic service, in addition to their own household and childcare responsibilities. The activities of the not-working women were largely restricted to household and childcare responsibilities. The working women tended to spend less time in resting activities and TV-watching and more time in travel and miscellaneous work activities, but other between-group differences were not significant. We conclude that the time allocation of working women is similar to that of not-working women because 1) many of the activities engaged in are the same or similar, and 2) some working women are only engaged in income-earning activities for limited time periods.

Comparative and evolutionary dimensions of the energetics of human pregnancy and lactation.

The purpose of this article is to compare the energetics of reproduction for human and other primates in order to evaluate the extent to which human reproductive energetics are distinct from other primates and other large-bodied placental mammals. The article also evaluates the energetics of human and primate gestation and lactation using data from a variety of different populations living under different environmental circumstances. Energetics refers to energy intake and expenditure, and changes in body fat stores. Human and nonhuman primates have longer periods of gestation and lactation and slower prenatal and postnatal growth than other mammals of similar size. This reduces daily maternal energy costs. The development of sizable fat stores is not unique to humans, but fat stores are typically greater in human females and may play a greater role in reproduction. The strategies used to meet the energy costs of pregnancy vary among populations of humans and nonhuman primates and among humans interindividual variability is high. In pregnancy, some increase energy intake but others apparently do not. Increases in metabolic efficiency are evident in some human populations, whereas decreases in physical activity occur, but are not seen in all human or primate populations. Lactation is more energetically costly on a daily basis among humans and nonhuman primates, but has not been as well studied. It appears that both nonhuman and human primates tend to increase energy intake to meet in part the cost of lactation. They also use other strategies such as relying on body tissue stores, reductions in physical activity, and/or increases in metabolic efficiency to meet the remainder of the cost. It is also clear that human females in different populations and different women in the same population use a different combination of strategies to meet the cost of lactation.

Energy intake and expenditure of free-living, lactating Colombian women in an urban setting.

OBJECTIVES: To examine the components of energy balance during lactation in a population of economically disadvantaged women in an urban developing country setting in order to better understand the metabolic response to lactation. DESIGN: Cross-sectional comparison of lactating (LACT) and non-pregnant non-lactating (NPNL) women. Body size and composition were assessed via anthropometry, energy intake was measured using estimated diet records and energy expenditure using indirect calorimetry and the Flex-Heart Rate method. SETTING: Low-income neighborhoods of Cali, Colombia. SUBJECTS: Lactating women (n=15) studied at 2.4+/-0.8, 5.5+/-0.8 and 8.9+/-1.2 months postpartum, and NPNL women (n=48) studied in three measurement rounds at 0, 3.5+/-0.6 and 7.1+/-1.0 months. RESULTS: There were no significant differences between LACT and NPNL women in anthropometric dimensions, but LACT women showed decreases in waist-hip ratio, lean body mass and increases in mid-arm circumference and percentage body fat with time. Energy intake was higher in LACT women (P=0.04), but there were no significant between-group differences in energy expenditure variables. CONCLUSION: This group of women met the cost of lactation principally via increased energy intake.

A comparison of anthropometric indices of nutritional status in Tukanoan and Achuar Amerindians.

Anthropometric data from a Tukanoan population in the Vaupes region of Colombia and an Achuar population in the Ecuadorian Amazon were compared relative to international references. The Tukanoans exploit an oligotrophic blackwater ecosystem, whereas the Achuar inhabit a resource rich montane ecosystem. Given this ecological distinction, three hypotheses regarding nutritional statuses were proposed: (1) Tukanoans are significantly shorter than the Achuar, indicating a greater degree of stunting; (2) Tukanoans are significantly leaner, indicating a greater degree of wasting; and (3) Tukanaons have significantly lower upper arm muscle area, indicating lower lean body mass. Z-scores for height, weight-for-height, and estimated upper arm muscle area were determined and significant nutritional stress was assumed at z < or = -2.0. Between population differences in z-scores for height-for-age (ZHT), weight-for-height (ZWH), and upper arm muscle area (ZUMA) were examined using analysis of variance with a subsequent Scheffe's test. Between-group differences in the frequencies of individuals with low z-scores (z < or = -2.0) were assessed via chi-squared analysis. Both populations showed stunting in most age groups, but neither showed low ZWH or ZUMA. Significant differences between populations were found only for ZHT in children (females 1.0-4.9 and 5.0-9.9 years, and males 5.0-9.9 years). Tukanoans have significantly higher frequencies of stunting in all age-sex groups except females and males age 30-49.9 years. There were no significant between-population differences in the frequencies of individuals with low ZWH or ZUMA. These differences in nutritional status may reflect differences in resource availability.

The importance of leaf- and litter-feeding invertebrates as sources of animal protein for the Amazonian Amerindians.

At least 32 Amerindian groups in the Amazon basin use terrestrial invertebrates as food. Leaf- and litter-consuming invertebrates provide the more important, underestimated food sources for many Amerindian groups. Further, litter-consuming earthworms are also an important food resource for the Ye'Kuana (also known as Makiritare) in the Alto Orinoco (Amazonas, Venezuela). By selecting these small invertebrates the Amerindians are choosing their animal food from those food webs in the rainforest which have the highest energy flow and which constitute the greatest renewable stock of readily available nutrients. Here we show that the consumption of leaf- and litter-feeding invertebrates as a means of recovering protein, fat and vitamins by the forest-living peoples offers a new perspective for the development of sustainable animal food production within the paradigm of biodiversity maintenance.

Energy intake and expenditure of free-living, pregnant Colombian women in an urban setting.

BACKGROUND: This study examined the components of energy balance in poor, free-living pregnant women living in an urban setting of a developing country. OBJECTIVES: We tested the following hypotheses: 1) energy intake increases in pregnancy and is greater than when nonpregnant and nonlactating (NPNL), 2) basal metabolic rate (BMR) increases in pregnancy and the increase is positively correlated with prepregnancy fatness, and 3) energy expenditure in activity decreases in pregnancy and is lower than in NPNL women. DESIGN: Pregnant women were studied at 14.8 +/- 3.4 (n = 40), 25.0 +/- 3.2 (n = 54), and 34.9 +/- 2.4 (n = 43) wk gestation, and NPNL women at baseline (n = 114) and at 3 (n = 103) and 6 (n = 93) mo. Energy intake was measured by using estimated diet records and energy expenditure by using the flex heart rate method. Time allocation in physical activity was assessed by observation. RESULTS: In pregnant women, body weight, BMR, and energy intake increased but total daily energy expenditure (TDEE) did not change significantly. There were no significant changes in time allocation to selected activities except for lying down. In comparison with NPNL control subjects, women in late pregnancy had higher energy intakes and BMRs. Values for TDEE were not significantly different, but pregnant women expended less energy in activity and allocated more time to 2 energy-saving activities and less time to 2 energy-demanding activities. CONCLUSION: A decrease in energy expenditure in activity and changes in time allocation are important ways in which pregnant women meet the energy demands of pregnancy.

Estimating energy intake of urban women in Colombia: comparison of diet records and recalls.

As part of a larger study of energy-nutrition, we compared the performance of 24 h diet recalls with estimated diet records kept by trained observers. The subjects were economically disadvantaged women (n = 85) in the city of Cali, Colombia. A 24 h recall and an estimated diet record were collected for each woman at 0 and approximately 3 and 6 months. Energy intake obtained from the estimated dietary records was validated against energy expenditure and used as the reference method. Energy and macronutrient intake were calculated from published food composition tables and proximate analyses of common foods. The number of food items consumed per woman per day, total and in each of 16 food groups, was tabulated. Energy and macronutrient intakes were 11-13% lower in the 24 h recalls. The discrepancy energy could be largely accounted for by the lower number of food items in the recalls. The number of food items in eight of 16 food groups was significantly lower in the recalls compared to the records. Underreporting on the recalls was a general tendency in these subjects and not clearly related to average energy intake. We conclude that 24 h diet recalls underestimate energy and nutrient intake in this population and are not suitable for studies of human energetics.

Gastrointestinal parasitic infection, anthropometrics, nutritional status, and physical work capacity in Colombian boys.

This article tests the hypothesis that the presence of gastrointestinal parasites in Colombian boys is negatively associated with anthropometric characteristics, physical work capacity, blood hemoglobin (Hb) levels, and nutritional status. Anthropometric, Hb, &Vdot;O(2) max, and parasite load data were collected on 1,016 boys in Cali, Colombia. The boys were classified as lower socioeconomic class (SEC) from either urban or rural environments, and upper SEC from an urban environment. Sixty-three percent of the boys were infected with gastrointestinal parasites and, of the infected boys, 80-95% had light parasite loads. Parasites found included Necator americanus, Ascaris lumbricoides, Entamoeba histolytica, Trichuris trichiura, Giardia spp., and Enterobius vermicularis. Infected boys had significantly lower weight, stature, weight-for-height (among 6-9-year-old boys), Hb levels, and &Vdot;O(2) max (ANCOVA, controlling for age and SEC). In terms of nutritional status, infected boys were 1.47 times more likely to be classified as iron deficient than noninfected boys (chi-square, P < 0.001), and 1.61 times more likely to be classified as stunted (P < 0.001). Infection was not associated with wasting in any SEC group. In conclusion, light to moderate gastrointestinal parasite loads were associated with significantly lower weight, stature, weight-for-height (in 6-9-year-old boys), Hb levels, and &Vdot;O(2) max, and a significantly higher frequency of IDA and stunting. These data suggest that comprehensive analyses of the nutritional status of populations in regions endemic for parasitic infection should include testing for the presence of infection. Am. J. Hum. Biol. 11:763-771, 1999. Copyright 1999 Wiley-Liss, Inc.

Increased muscular efficiency during lactation in Colombian women.

OBJECTIVE: To determine the muscular efficiency of lactating women and compare it to that of nonpregnant, nonlactating (NPNL) women. DESIGN: The study was retrospective. The subjects were selected randomly in the two groups and studied on three occasions (rounds) separated by approximately three months. SUBJECTS: There were 109, 101, and 80 NPNL women and 45, 31 and 16 lactating women in rounds 1, 2 and 3 respectively, 19-43 y of age, living under economically deprived conditions in Cali, Colombia, who participated in the study. METHODS: Muscular efficiency was measured as delta efficiency on a cycle ergometer. RESULTS: Muscular efficiency was significantly higher in lactating women in all three rounds compared to NPNL women. In six women it was possible to measure efficiency at variable times prior to their pregnancies, and again during lactation about three months post partum. There was a statistically significant (P = 0.03) increase in muscular efficiency during lactation. CONCLUSION: Lactation results in about a 5% increase in muscular efficiency which may contribute to the adaptation of the mother to the increased energy demands associated with lactation.

PIP: The muscular efficiency of low-income lactating women living in Cali, Colombia, was compared to that of nonpregnant, nonlactating women from the same neighborhoods in a retrospective study that involved 3 rounds separated by about 3 months. Rounds 1, 2, and 3 (occurring at an average of 2.4, 5.3, and 8.6 months postpartum) included 109, 101, and 80 nonpregnant, nonlactating women, respectively, and 45, 31, and 16 lactating women, respectively. Muscular efficiency, measured as delta efficiency on a cycle ergometer, was significantly higher among lactating than nonlactating, nonpregnant women in all 3 rounds. In the 6 women in whom it was possible to measure muscular efficiency at variable times prior to their pregnancy as well as at 3 months postpartum, there was a statistically significant increase in muscular efficiency during lactation. Overall, lactation resulted in about a 5% increase in muscular efficiency. This phenomenon may contribute to the adaptation of the mother to the increased energy demands associated with breast feeding.

Daily energy expenditure of women by factorial and heart rate methods.

To compare the minute-by-minute heart rate (Flex-HR) reference method with the factorial method, total daily energy expenditure (TDEE) and the pattern of daily energy expenditure (EE) were measured in nonpregnant, nonlactating women 19-40 yr of age, working at their household chores (at home, N = 20) or for remuneration in various kinds of employment (at work, N = 28). The factorial method used three data sets described in the compendium of Ainsworth et al. (CMD), FAO/WHO/UNU (FAO), and James and Schofield (J&S). Measurements were repeated on three rounds separated by 3 months. The TDEE by Flex-HR method, by round, was 9.0 +/- 2.6, 8.9 +/- 1.4, and 10.3 +/- 3.4 MJ.d-1 in the women at home and 9.7 +/- 2.3, 11.4 +/- 3.2, and 11.3 +/- 3.6 MJ.d-1 in the women at work. Values using the CMD data set were not significantly different from Flex-HR in either group in any round, but FAO and J&S data sets gave significantly lower values than both of the former methods in all rounds. The same statistical results were obtained for the patterns of activity. Since the timing of activities by the observers was the same, it is concluded that the major source of error in applying the factorial method is in the values for energy expenditure assigned to the various activities and the ability of investigators to properly judge EE from available data sets.

Understanding the nutrition of poor urban women: ethnographic and biological approaches.

To better understand how women respond to conditions of urban poverty in a developing country a sample of 85 women living in Cali, Colombia was studied. Anthropometric indicators of nutritional status were normal for the group. However, many women indicated that they did not always have sufficient money to purchase food, and described the strategies they used when financial resources were inadequate. These strategies included changes in meal composition, reductions in food portion size, and reductions in the number of meals eaten. Evidence of the use of these strategies was identified in 17.1% of all diet records (n = 509). The adequate nutritional status of this group of women suggests that their strategies were usually successful in maintaining adequate energy intake, but the frequent use of these strategies suggests that the women are potentially at risk for undernutrition.

Living on the edge: dietary strategies of economically impoverished women in Cali, Colombia.

Economically impoverished women in Cali, Colombia, have restricted access to food in a city where food is abundant. Ethnographic observations, interviews and 2 day food records were used to better understand the coping strategies used by a group of these women (n = 85) to maintain adequate levels of energy intake. Anthropometric indicators of nutritional status were normal for the group. Interview data revealed that the ability to purchase food was a concern for 58% of the women. When faced with a restricted ability to purchase food, the women indicated they made compromises in meal composition, reduced portion sizes, and/or reduced the number of meals. They also relied on relatives, friends, neighbors, store credit, or local government programs for access to food. Changes in meal composition were identified in 17.1% of all diet records (n = 509). Low energy intake (defined as energy intake < or = 1.27 x BMR) was identified in 17.1% of all diet records. Carbohydrate consumption was significantly greater on low-energy intake days. The adequate nutritional status of this group of women suggests that their coping strategies are usually adequate to maintain energy intake, but the presence of uncertainty, the frequency of compromises in diet composition, and the frequency of low-energy intake days suggest that these women are at risk for undernutrition.

Energy expenditure of urban Colombian women: a comparison of patterns and total daily expenditure by the heart rate and factorial methods.

The heart rate and factorial methods of measuring both total daily energy expenditure (TDEE) and the daily pattern of energy expenditure (EE) were compared in nonpregnant, nonlactating women aged 19-43 y living in urban conditions of economic deprivation. The methods were applied on each of 2 successive days. There were no significant differences between the 2 d by either method. Women who worked at their household chores at home (n = 29) and those who also worked for remuneration (at work) in various kinds of employment (n = 23) were compared. The factorial method gave values for TDEE and for the pattern of EE that were significantly lower than those obtained by the heart rate method. This was related to lower values for EE for certain activities obtained from the literature than for values measured in these subjects. Women at work had significantly higher values for both TDEE and for the pattern of EE than did those at home. The TDEE at home by the heart rate method was 8.83 +/- 1.94 MJ/d and at work was 9.99 +/- 1.91 MJ/d (P = 0.036); this difference disappeared when adjusted for body weight or fat-free mass. Physical activity levels were 1.83 +/- 0.43 for women at home and 1.90 +/- 0.46 for women at work, which indicate moderate to heavy work. The factorial method should be used with measured EE values in the present subject population. The heart rate method can detect differences in TDEE and in the pattern of EE between women engaged in different activities and may offer an experimental approach to the study of the effects of daily variations in EE on nutritional energy intake.

Body composition of Colombian women.

Measurements of anthropometry and total body water (TBW) were made in 99 women 19-44 y of age living in socioeconomically deprived circumstances in Cali, Colombia. TBW was measured by dilution of deuterium oxide. An empirical equation for estimating lean body mass (LBM) was derived and applied satisfactorily to an independent study group. Comparisons were also made with body-composition values obtained by the Durnin and Womersley equations and an equation derived from rural women living in Guatemala. Neither set of equations was suitable for use with the Colombian subjects because both significantly overestimated LBM and therefore underestimated body fat. Lower values of standing height in older women suggest that they may have been subjected to more severe undernutrition during their growth than the younger subjects. When compared with a group of US women, Colombian subjects were less physically fit and had greater subcutaneous-fat deposits, which were distributed over the trunk and limbs, whereas body mass indexes and waist-hip ratios were not significantly different.

Variation of the basal metabolic rate and dietary energy intake of Colombian women during 1 y.

Anthropometry, basal and resting metabolic rates (BMR and RMR), and dietary energy intake were measured on five occasions approximately 3 mo apart for 1 y in 21 nonpregnant, non-lactating women 20-42 y of age living under deprived economic conditions in Cali, Colombia. There was a significant increase in body weight (1-1.5 kg) because of increased body fat during the last two rounds of measurement. BMR was elevated in the first round but fell to stable values that did not vary significantly from 3 to 12 mo. The intraindividual CV of BMR was 8.3% whereas the intraindividual CV of dietary energy intake was 17%. Measured BMR was closely related to the BMR estimates provided by the empirical equations of Schofield, but significantly higher than estimates from the equations of Henry and Rees. RMR-BMR ratios were very close to those published by FAO/WHO/UNU. Autocorrelation analysis of BMR showed weak ability to predict subsequent variation of BMR over time and is consistent with random variation of the data.

Anthropometry and secular changes in stature of urban Colombian women of differing socioeconomic status.

Anthropometric dimensions were taken on 1,572 women, 18-44 years of age, from Cali, Colombia, from three different socioeconomic (SEC) groups: low (LEC), mid-low (MLEC), and upper (UEC). LEC and MLEC women were significantly shorter and had higher body mass indices (BMIs) than UEC women, and a significantly larger number had BMIs over 27.3 kg/m2 . There were no significant differences between SEC groups for skinfolds on the arm, but skinfolds on the trunk, the subscapular-triceps ratio, and the waist-hip ratio followed an inverse SEC gradient, indicating a greater tendency for upper body fat distribution in the lower SEC groups. SEC differences in body fatness and fat distribution diminished with age, suggesting that health risks associated with obesity and an upper body fat distribution may be similar in all three groups by ages 40-44 years. Secular changes in stature were similar, 0.12 cm/year for LEC/MLEC women and 0.15 cm/year for UEC women, and there was no indication that the statural differences between the groups is diminishing. The results indicate that women from Cali exhibit anthropometric characteristics seen in both developing countries (stature positively associated with SEC) and developed countries (fatness and centralized fat distribution inversely related to SEC). These findings may reflect the relative economic prosperity of Colombia as a "developing country". © 1994 Wiley-Liss, Inc.

V̇ O 2 max and nutritional status in Urban Colombian girls and women.

Maximal oxygen consumption (V̇ O 2 max, liters min-1 ) was measured in 60 nutritionally normal and 74 marginally undernourished girls 6-16 years of age and 27 upper socioeconomic (UEC) women and 22 women living in economically deprived conditions (LEC) in Cali, Colombia. All girls were recruited from the LEC neighborhoods. Lower values for V̇ O 2 max (liters min-1 ) in undernourished girls were replaced by a nutritionally normal status in adulthood in which V̇ O 2 max was not significantly different from that measured in UEC women. Physical condition varied from average to fair in the younger to older subjects compared to women from industrialized countries. When V̇ O 2 max is expressed as ml min-1 kg-1 of lean body mass (LBM), all age and group effects disappear, confirming regression analysis which demonstrated a close relationship (r2 = 0.81) between V̇ O 2 max (liters min-1 ) and LBM in which there were no significant differences between nutritional or socioeconomic groups. © 1994 Wiley-Liss, Inc.

Maximal oxygen consumption of Colombian women of differing socioeconomic status.

Maximal oxygen consumption (\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot V}_{{\rm O}_2 } $\end{document} max) was measured directly by a treadmill protocol in 23 upper (UEC) and 23 lower (LEC) socioeconomic women, 19-37 years of age, living in Cali, Colombia. There were no statistically significant differences between the two groups in \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot V}_{{\rm O}_2 } $\end{document} max (liters/min). LEC women were shorter and weighed less than UEC subjects, although there was no evidence of undernutrition in the former at the time of testing. The aerobic power of the LEC group was 33.7 ± 4.1 ml/kg · min (mean ± SD) compared to 32.0 ± 2.8 ml/kg · min in UEC women (P = 0.09). From data on 36 of the women, a multiple stepwise regression was used to derive an empirical equation for estimating \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot V}_{{\rm O}_2 } $\end{document} max from submaximal \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot V}_{{\rm O}_2 } $\end{document} and heart rate plus anthropometric variables. The derived equation was verified by application to an independent group of 10 subjects. © 1992 Wiley-Liss, Inc.