Energy requirements of pregnancy in The Netherlands.

57 healthy Dutch women were studied longitudinally from early pregnancy until 2 months post partum. Regular measurements were made of energy intake in food, basal metabolic rate, body weight and body fat mass, and levels of physical activity. Some data were obtained before conception in 23 women. The energy cost of pregnancy calculated as the energy deposited as new tissues plus the associated increase in basal metabolism amounted to 286 MJ (1020 kJ/day), which is only 11% lower than the theoretical estimate of requirements of 323 MJ (1 MJ = 239 kcal). Energy intake throughout the first 10 wk of pregnancy was identical to that before pregnancy. Energy intake was only 200 kJ/day higher in late than in early pregnancy (not significant), and the cumulative increase in energy intake over pregnancy was estimated as 22 MJ (about 80 kJ/day). There is, therefore, an energy gap in pregnancy of about 940 kJ/day. It is proposed that the main mechanisms by which the pregnant body is able to save energy and to bridge the energy gap are by adjustments to physical activity and an increase in work efficiency and an adaptation of the metabolic response to food. Savings on physical activity by behavioural adaptations will not exceed 355 kJ/day.