Resting metabolic rate and body composition of healthy Swedish women during pregnancy.

Body weight, resting metabolic rate (RMR), total body potassium (TBK), and total body water were measured and total body fat (TBF) was calculated in a longitudinal study of 22 pregnant, healthy Swedish women. Measurements were made before pregnancy, at gestational weeks 16-18, 30, and 36, and 5-10 d and 6 mo postpartum. RMR increased more during pregnancy than previous estimates on well-nourished women showed and the increase was significantly correlated with the birth weight of the baby. TBK decreased during the first part of pregnancy; measurements at weeks 16-18 and 30 were significantly lower than the prepregnancy value and changes in TBK and RMR were significantly correlated. TBF gain during pregnancy was 5.8 +/- 4.0 kg and 60% was already gained by gestational weeks 16-18. Gain in fat was not correlated with birth weight.

Estimation of body fat in healthy Swedish women during pregnancy and lactation.

Reliable estimates of changes in body fat are important in studies of energy requirements during human reproduction. It is not known if current methods for the estimation of total body fat (TBF) are adequate for this purpose. In this paper earlier reported data from 29 women are used to show how methodology affects estimates of changes in TBF during reproduction. Skinfold thicknesses are also reported and equations relating these measurements to TBF were developed and used to demonstrate how well the skinfold technique could estimate such changes. No correlation was found between changes in body weight and body fat during early pregnancy or between the maternal changes in body weight and body fat over the complete pregnancy. These findings are tentatively explained by changes in the degree of hydration of the body.

Energy metabolism, body composition, and milk production in healthy Swedish women during lactation.

Variables of relevance to energy requirements during reproduction were studied in 23 healthy lactating Swedish women. Body composition and resting metabolic rate (RMR) were studied before pregnancy and three times postpartum. Energy intake was studied before pregnancy and, together with breast-milk production, 2 mo postpartum. The women gained 5.8 +/- 4.2 kg fat during pregnancy and their average fat content was unchanged during the first 2 mo of lactation whereas a slight loss (1.7 +/- 4.2 kg) occurred during the following 4 mo. RMR increased slightly during lactation in spite of a decrease in fat-free body weight 2 and 6 mo postpartum. Energy intake increased during lactation (280 +/- 440 kcal/d). The women produced 740 +/- 150 g breast milk/d containing 0.64 +/- 0.08 kcal/g. The results indicate that current estimates of energy needs during lactation may be too high.

Total energy expenditure of healthy Swedish women during pregnancy and lactation.

Total energy expenditure (TEE) was estimated in healthy Swedish women by the doubly labeled water method in a longitudinal study during pregnancy and lactation. Measurements were made before pregnancy (A); in gestational weeks 16-18 (B), 30 (C), and 36 (D); as well as 2 (F) and 6 (G) mo after delivery. When the results were interpreted, earlier published data regarding resting metabolic rate (RMR), energy intake, and energy in breast milk were also considered. TEE (MJ/d) and TEE/RMR were 10.5 +/- 2.2 (mean +/- SD) and 1.87 +/- 0.42 (n = 28), 9.6 +/- 2.8 and 1.65 +/- 0.67 (n = 22), 12.5 +/- 3.4 and 1.82 +/- 0.45 (n = 22), 12.2 +/- 4.1 and 1.66 +/- 0.52 (n = 19), 10.6 +/- 2.0 and 1.82 +/- 0.41 (n = 23), and 10.8 +/- 2.7 and 1.79 +/- 0.42 (n = 23) at A, B, C, D, F, and G, respectively. The results indicated that physical activity tended to be decreased during early pregnancy. Taking changes in body energy stores into consideration, it was estimated that subjects recorded 86% and 77% of their energy intakes at A and F respectively.

Growth, body composition and breast milk intake of Swedish infants during early life.

The growth and breast milk intake of 22 healthy completely breast fed Swedish infants (9 girls, 13 boys) during the first 10 wk of life are reported and were found to be similar to those of other healthy breast fed populations of infants. Also the body composition (body fat and lean body tissue) was estimated by an anthropometric method at the age of about 10 and 65 days. It was found that the breast milk intake correlated significantly with weight and fat gain but not with gain in lean body tissue or with gain in length. These findings suggest that energy rather than protein intake limited growth in this group of infants. Also the results confirm the fact that the capacity for fat retention is high during early life and show that the size of fat stores is related to breast milk intake.

Energy restriction and the partitioning of energy among the costs of reproduction in rats in relation to growth of the progeny.

Compared with well-nourished controls, progeny of energy-restricted females are smaller and grow less well. The mechanisms behind these effects are frequently studied in rats but interpretation of such studies requires knowledge about the partitioning of dietary energy among the costs of reproduction and maternal needs. Energy partitioning was studied in rats fed ad libitum or 70% of ad libitum intake from 24-34 d before conception until d 14 of lactation and in virginal controls. Body composition was estimated for adult rats on d 1 of gestation, for adult rats and litters on d 1, 9 and 14 of lactation and for virginal controls after 65 d of dietary treatment. Milk production and composition were also studied. Dams in the two groups retained similar amounts of energy during pregnancy. Mobilized body energy corresponded to only 6 and 12% of the energy in milk for ad libitum-fed and restricted rats, respectively. Adult energy-restricted rats were smaller than their ad libitum-fed counterparts and thus needed less energy for maintenance. During lactation, energy-restricted rats used less energy per unit body size than ad libitum-fed rats. Pups of restricted dams were not only smaller, they also utilized milk energy less efficiently than did pups of well-fed dams.

Polyunsaturated fatty acids recruit brown adipose tissue: increased UCP content and NST capacity.

To examine the effect of polyunsaturated fatty acids (PUFA) on brown adipose tissue recruitment and on the capacity for nonshivering thermogenesis (NST), mice were fed a diet with a standard fat content (9%) and a normal PUFA content (1.6%) (controls) or a high-PUFA content (4.3%) for 2-3 wk. The resting metabolic rate was somewhat lower in the high-PUFA group, probably due to a lower physical activity whereas the capacity for NST (estimated as the metabolic response to a norepinephrine injection) was higher in the high-PUFA group. There was no significant effect on brown adipose tissue wet weight, protein content, or cytochrome-c oxidase content, but the amount of the uncoupling protein thermogenin (UCP), measured immunologically, was significantly increased in the high-PUFA mice (totally by 41%). It was concluded that short-term feeding of a high-PUFA diet may recruit brown adipose tissue thermogenic capacity; it was speculated that earlier-reported recruiting effects of high-fat diets may not be due solely to the high total fat content of the diet but perhaps also to a specific recruiting property of the high-PUFA diets generally used in this type of investigation.

Body composition and fat distribution during the first 2 weeks of gestation in ad lib.-fed and energy-restricted rats.

Knowledge about changes in body composition during gestation is of interest when estimating energy requirements during pregnancy, and relevant since reproduction is often surprisingly well maintained in malnourished females. Due to difficulties in conducting such studies in humans, studies in rats are of interest. Therefore, maternal retention of fat and fat-free weight was estimated in rats during the first 2 weeks of gestation and during a corresponding time period in virgin controls. Groups fed ad lib. or 70% of ad lib. intake during the 4 weeks preceding conception and during gestation were studied. Retention was estimated by comparing pregnant and virgin rats with rats killed at the time of conception. Body fat was analysed chemically and fat-free weight was body weight minus body fat. Each rat was divided into twelve to fourteen parts and the fat content of each part was analysed. Pregnant ad lib.-fed rats retained more fat and fat-free weight than did virgin ad lib.-fed controls. In the energy-restricted group the pregnant rats retained more fat-free weight while virgin rats retained slightly more fat than did pregnant rats. The difference between pregnant and virgin rats with respect to the amount of fat in the different body parts was small in both feeding groups. Thus, the statement that fat stored at specific sites in the maternal body represents an important source of energy for use during lactation was not supported. The findings suggest that pregnancy stimulates growth of the maternal body and that chronic moderate energy restriction curtails this growth.