Abstract
BACKGROUND: African-American (AA) women have poorer pregnancy outcomes, and studies in nonpregnant women suggest a different etiology of weight gain in AA compared with white women. We hypothesized that physiologic factors such as low energy expenditure and physical activity would be present in AA compared with white women in pregnancy. OBJECTIVE: We aimed to identify physiologic risk factors for disordered energy balance in AA and white women early in pregnancy. DESIGN: This was a cross-sectional study in 66 pregnant women with obesity, between 14 and 16 wk of gestation. Energy intake was calculated using the intake-balance method. Energy expenditure was measured in free-living conditions [total daily energy expenditure (TDEE)] over 7 d with the use of doubly labelled water and during sleep [sleeping EE (SleepEE)] in a room calorimeter. Body composition was measured by air displacement plethysmography and physical activity by accelerometers. Markers of metabolic health were obtained from fasting blood and urine. RESULTS: AA (n = 34) and white (n = 32) women were comparable in age (mean ± SEM: 27.7 ± 0.6 y), enrollment body mass index [mean ± SEM (in kg/m2): 36.9 ± 0.7], and body fat (mean ± SEM: 45.0% ± 0.6%). AA women had more fat-free mass (P = 0.01) and tended to be more insulin-resistant (homeostasis model assessment of insulin resistance, P = 0.06). Energy intake was significantly lower in AA than in white women (2499 ± 76 compared with 2769 ± 58 kcal/d, P = 0.001), although absolute TDEE was comparable (AA: 2590 ± 77 kcal/d; white: 2711 ± 56 kcal/d; P = 0.21). After adjusting for body composition, TDEE was significantly lower in AA women (-231 ± 74 kcal/d, P = 0.003), as was SleepEE (-81 ± 37 kcal/d, P = 0.03). Physical activity, substrate oxidation, and metabolic biomarkers (triiodothyronine and thyroxine concentrations, catecholamine excretion) were not significantly different between groups. CONCLUSIONS: Body mass-adjusted energy expenditure is significantly lower in AA than in white pregnant women. Energy intake recommendations for pregnancy do not consider this difference and may therefore overestimate energy requirements in AA women. This may lead to unintentional overeating and contribute to the disparity of excess gestational weight gain and postpartum weight retention that is more prevalent in AA women. This trial was registered at clinicaltrials.gov as NCT01954342.