Energy Expenditure in Pregnant Women with Obesity Does Not Support Energy Intake Recommendations

OBJECTIVE: Identify factors that may predispose to excess gestational weight gain (GWG). METHODS: Seventy-two healthy women with obesity (30 Class I, 24 Class II, 18 Class III) expecting a singleton pregnancy were studied at 13-16 weeks gestation. Energy expenditure (EE) was measured during sleep (SleepEE, average EE from 0200-0500h) in a whole-room calorimeter, and total daily EE (TDEE) over seven days using doubly-labeled water. Glucose, insulin, thyroid hormones and catecholamines were measured. RESULTS: Body composition explained 70% variability in SleepEE, and SleepEE accounted for 67-73% of TDEE. While there was no evidence of consistent low metabolism, there was considerable variability. Low SleepEE was associated with insulin resistance and low T3 concentrations (both, p=0.01). Physical activity level was 1.47±0.02. For women with SleepEE within 100kcal/d of their predicted EE, TDEE was significantly less than the estimate (2530±91 vs. 2939kcal/d, p<0.001) provided from the most recent gestational energy requirement model. CONCLUSIONS: Pregnant women with obesity are inactive, possibly predisposing them to excess GWG. Current energy requirement models overestimate activity and may promote excess GWG in women with obesity. Further, we speculate that the observed large inter-individual variability in basal metabolism may be important to consider when assessing the risk for excess GWG.