title: Changes in resting and walking energy expenditure and walking speed during pregnancy in obese women.
abstract: BACKGROUND
  Energy-conserving processes reported in undernourished women during pregnancy are a recognized strategy for providing the energy required to support fetal development. Women who are obese before conceiving arguably have sufficient fat stores to support the energy demands of pregnancy without the need to provoke energy-conserving mechanisms.
  
  
  OBJECTIVE
  We tested the hypothesis that obese women would show behavioral adaptation [ie, a decrease in self-selected walking (SSW) speed] but not metabolic compensation [ie, a decrease in resting metabolic rate (RMR) or the metabolic cost of walking] during gestation.
  
  
  METHODS
  RMR, SSW speed, metabolic cost of walking, and anthropometric variables were measured in 23 women aged 31 ± 4 y with a BMI (in kg/m(2)) of 33.6 ± 2.5 (mean ± SD) at ≈15 and 30 wk of gestation. RMR was also measured in 2 cohorts of nonpregnant control subjects matched for the age, weight, and height of the pregnant cohort at 15 (n = 23) and 30 (n = 23) wk.
  
  
  RESULTS
  Gestational weight gain varied widely (11.3 ± 5.4 kg), and 52% of the women gained more weight than is recommended. RMR increased significantly by an average of 177 ± 176 kcal/d (11 ± 12%; P < 0.0001); however, the within-group variability was large. Both the metabolic cost of walking and SSW speed decreased significantly (P < 0.01). Whereas RMR increased in >80% of the cohort, the net oxygen cost of walking decreased in the same proportion of women.
  
  
  CONCLUSIONS
  Although the increase in RMR was greater than that explained by weight gain, evidence of both behavioral and biological compensation in the metabolic cost of walking was observed in obese women during gestation. The trial is registered with the Australian Clinical Trials Registry as ACTRN012606000271505.
authors.affiliation: School of Human Movement Studies, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia. n.byrne@qut.edu.au
authors.forename: Nuala M
authors.initials: NM
authors.lastname: Byrne
authors.forename: Ainsley M
authors.initials: AM
authors.lastname: Groves
authors.forename: H David
authors.initials: HD
authors.lastname: McIntyre
authors.forename: Leonie K
authors.initials: LK
authors.lastname: Callaway
mesh_terms: D000328:Adult; D001481:Basal Metabolism; D001519:Behavior; D015992:Body Mass Index; D016022:Case-Control Studies; D015331:Cohort Studies; D004734:Energy Metabolism; D005260:Female; D005684:Gait; D006801:Humans; D009765:Obesity / Q000378:metabolism*; D010101:Oxygen Consumption; D011247:Pregnancy; D011248:Pregnancy Complications / Q000378:metabolism*; D012146:Rest; D016138:Walking; D015430:Weight Gain