Submitted to: Journal of Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/10/1996
Publication Date: N/A
Citation: Interpretive Summary: We wanted to know how low- to moderate-weight women in poor countries get the extra energy they need for lactation: from eating more food, from stored body fat, reducing their activities, or increasing the efficiency of their metabolism. We studied 40 rural Mesoamerindian women after they gave birth and put them in two groups based on low vs moderate body mass index. Both groups participated in normal, low to moderate physical activity; the lower-weight women were more active after adjusting for body weight. Lactation performance did not differ between groups, and was not affected by the level of physical activity or total energy expenditure. Total energy requirements were similar between groups. The groups did not conserve energy in the face of heightened requirements for milk production. These findings are important in figuring dietary recommendations for lactating women, and evaluating allocation of limited resources in poor countries.
Technical Abstract: Energy-sparing mechanisms may be elicited to meet increased energy requirements imposed by lactation on women who reside in poor, rural communities in developing countries. The objectives of this study were to measure total energy expenditure and its components, basal and activity energy expenditure, and to investigate their effects on lactation performance in a total of 40 rural Mesoamerindians grouped according to lo or moderate body mass index. Total energy expenditure and fat-free mass were measured by the doubly labeled water method, and basal metabolic rate was determined by indirect calorimetry at 3 and 6 mo postpartum. Physical activity level was taken as the ratio of total energy expenditure/basal metabolic rate. Milk energy output was computed from 24-h milk intake (test-weighing) and energy concentration of milk (bomb calorimetry). Anthropometric measurements revealed negligible mobilization of tissue stores. Mean (+/-SD) total energy expenditures were 8912+/-1296 kJ/d and 9253+/-1298 kJ/d for the low and moderate body mass index groups, respectively. Adjusted for fat-free mass, total energy expenditure was higher in the low body mass index group (P=0.05). Adjusted for fat-free mass, basal metabolic rate did not differ between groups. Physical activity level was significantly higher in the low body mass index group (P=0.03). Lactation performance did not differ between groups, and was not influenced by total energy expenditure or its components. Despite the maintenance of energy balance and heightened energy requirements of lactation, energy-spar echanisms were not evident in these lactating Mesoamerindians.