Energy cost of physical activity throughout pregnancy and the first year postpartum in Dutch women with sedentary lifestyles

Article Abstract:

Much research has been done to estimate the number of extra calories women need during pregnancy. It has been difficult to obtain accurate estimates because there are many interacting factors involved in a pregnant woman's energy needs, including her activity level, her energy stores before pregnancy, and the weight gained during pregnancy. The latest recommendation of the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) is an additional 285 calories per day, averaged over the course of the pregnancy. This amount should support the needs of women who begin pregnancy marginally underweight or undernourished and who do not reduce their physical activity during pregnancy. For healthy, well-nourished women who do reduce their activity, an average increase of 200 calories per day is recommended; the 85 calories subtracted primarily represents the savings for decreased physical activity. However, studies of women in both developing and developed countries have found that they generally increase energy consumption by less than the recommended amounts. This has led to the supposition that the amount of energy saved by reducing activity during pregnancy may be greater than previously thought. In this study, 25 sedentary Dutch women were assessed throughout pregnancy and the first year after the baby's birth; their activities, weight, and basal metabolic rate (energy used to maintain basic body functions while at rest) were measured. The assessment done at one year postpartum represented the nonpregnant, nonlactating state. It was found that compared with this time point, energy used for physical activity was reduced by an average of 70 calories/day during pregnancy and 50 calories/day in the first six months postpartum. Thus in these healthy, sedentary women, the amount of energy saved by reducing activity during pregnancy and lactation was modest, and was actually less than the 85 calories/day estimated by the FAO/WHO/UNU. Therefore, the amount of calories saved by decreasing physical activity does not explain why women in some studies have consumed less than the recommended increase in dietary energy for pregnancy. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Energy metabolism, Pregnancy

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Energy cost of lactation, and energy balances of well-nourished Dutch lactating women: reappraisal of the extra energy requirements of lactation

Article Abstract:

The energy cost of lactation, which consists of energy needed to produce the breast milk and energy content of the milk itself, has been estimated at 700 calories per day over the first six months after birth. But the additional energy requirements of lactation are often not met by well-nourished women, that is, they do not increase their food intake by this amount. It has been suggested that the energy cost of lactation may have been overestimated. In addition, breakdown of the mother's fat stores or reduced daily energy expenditure for activity can compensate for an increase in energy needs due to lactation. Energy expenditure can be reduced by lower physical activity and more efficient energy metabolism. The ability of well-nourished Dutch women to cope with the energy stress of lactation was assessed. Energy balance was evaluated by measuring food intake, body weight, body fat mass, levels of physical activity, basal metabolic rate, and breast milk production. In addition, the growth of the breast-fed infant was assessed to determine the adequacy of lactation. The energy intake of 40 lactating women at nine weeks after delivery was higher than that of 16 nonlactating women. Lactation required 650 calories per day, and lactating women tended to compensate for these extra energy needs by: eating more; using fat stores as an energy source; and reducing energy expenditure. These findings show how well-nourished women can meet the energy demands of lactation, and that current recommendations of energy requirements during breast-feeding are overestimated. (Consumer Summary produced by Reliance Medical Information, Inc.)

Nutrition, Nutritional requirements

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