title: Energy requirements during pregnancy based on total energy expenditure and energy deposition.
abstract: BACKGROUND
  Energy requirements during pregnancy remain controversial because of uncertainties regarding maternal fat deposition and reductions in physical activity.
  
  
  OBJECTIVE
  This study was designed to estimate the energy requirements of healthy underweight, normal-weight, and overweight pregnant women and to explore energetic adaptations to pregnancy.
  
  
  METHODS
  The energy requirements of 63 women [17 with a low body mass index (BMI; in kg/m(2)), 34 with a normal BMI, and 12 with a high BMI] were estimated at 0, 9, 22, and 36 wk of pregnancy and at 27 wk postpartum. Basal metabolic rate (BMR) was measured by calorimetry, total energy expenditure (TEE) by doubly labeled water, and activity energy expenditure (AEE) as TEE - BMR. Energy deposition was calculated from changes in body protein and fat. Energy requirements equaled the sum of TEE and energy deposition.
  
  
  RESULTS
  BMR increased gradually throughout pregnancy at a mean (+/-SD) rate of 10.7 +/- 5.4 kcal/gestational week, whereas TEE increased by 5.2 +/- 12.8 kcal/gestational week, which indicated a slight decrease in AEE. Energy costs of pregnancy depended on BMI group. Although total protein deposition did not differ significantly by BMI group (mean for the 3 groups: 611 g protein), FM deposition did (5.3, 4.6, and 8.4 kg FM in the low-, normal-, and high-BMI groups; P = 0.02). Thus, energy costs differed significantly by BMI group (P = 0.02). In the normal-BMI group, energy requirements increased negligibly in the first trimester, by 350 kcal/d in the second trimester, and by 500 kcal/d in the third trimester.
  
  
  CONCLUSIONS
  Extra energy intake is required by healthy pregnant women to support adequate gestational weight gain and increases in BMR, which are not totally offset by reductions in AEE.
authors.affiliation: US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA. nbutte@bcm.tmc.edu
authors.forename: Nancy F
authors.initials: NF
authors.lastname: Butte
authors.forename: William W
authors.initials: WW
authors.lastname: Wong
authors.forename: Margarita S
authors.initials: MS
authors.lastname: Treuth
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Ellis
authors.forename: E
authors.initials: E
authors.lastname: O'Brian Smith
mesh_terms: D000328:Adult; D001481:Basal Metabolism / Q000502:physiology*; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D009751:Nutritional Requirements; D011247:Pregnancy