Energy expenditure and consumption of mature, pregnant and lactating women.

Activity patterns, energy expenditure, and energy and protein consumption of mature women were determined during preganncy and lactation. Homemakers of average economic status from a mixed population were not significantly more active than teenage women, but the range of activities was greater. Average energy output for the latter half of gestation was 2,200 to 2,300 kcal per day; per unit of body weight, the mean was 32.5 +/- 4 kcal per kilogram for the twenty-week period. A small decline of 6 per cent in energy expenditure was noted near term. Allowing for deposition of fetal and material tissue, the average metabolizable energy need for this group was about 35 to 36 kcal per kilogram for the latter half of pregnancy. These data show that a pregnant woman of reference body weight (68 kg.) may vary in energy output by 800 to 900 kcal per day, depending on occupation. Homemakers with small children and especially those who work outside the home constitute a high energy work category. Thus, the need for considering work pace and work load, as well as body mass, in estimating the energy requirement during pregnancy was confirmed. Average daily energy intake reported was 1,955 kcal or 28.5 kcal per kilogram for the latter half of gestation. A mean protein intake of 1.17 gm. per kilogram per day represented 17 per cent of gross energy consumed. It is questionable whether the energy level consumed by these women was sufficient to maintain positive nitrogen balance on the days recorded. Lactating homemakers expended an average of 30 kcal per kilogram per day, exclusive of milk production. Energy intake was 30 kcal per kilogram, and was equal to 74 per cent of need when adjusted for milk production. Non-lactating women expended 34 kcal per kilogram per day, 13 per cent above the values for lactating women. Average energy intake of non-lactating women was 19 kcal per kilogram, with protein intake representing 19 per cent of energy consumed for both groups.