Propensity for excess gestational weight gain in African‐American women may be explained by hypometabolic factors in early pregnancy

Abstract

BackgroundWomen with obesity are at increased risk for excess gestational weight gain. Studies in non‐pregnant women suggest that the etiology of weight gain may be different between African‐American and White women and this may cause higher retention of weight postpartum and the increased prevalence of obesity in offspring.ObjectiveTo conduct a cross‐sectional study in African‐American and White pregnant women to identify metabolic and behavioral risk factors for aberrant weight gain trajectories.DesignMetabolic and behavioral phenotyping was conducted in 66 pregnant women with obesity, expecting a single fetus, between 14 and 16 weeks of gestation. Energy expenditure was measured in free‐living conditions over 7 days using stable isotopes and during sleep in a room calorimeter. Body composition was measured by air displacement plethysmography and physical activity by SenseWear™ accelerometers. Fasting blood was collected to measure markers of metabolic health.ResultsAfrican‐American (AA, n=34) and White women (W, n=32) were comparable in age (27.7±0.6 years) but had a lower socio‐economic status and higher parity. The two groups were matched for BMI (36.9±0.7 kg/m2) and while body fat was not different (55.1±0.6%), AA women had more fat‐free mass (AA: 56.9±1.6 vs W: 51.6±1.1 kg, p=0.009) and tended to be more insulin resistant (HOMA‐IR, AA: 4.0±0.4 vs W: 3.1±0.3, p=0.06). Total daily energy intake was significantly lower in AA women compared to their white counterparts (AA: 2633±88 vs W: 2901±76 kcal/d, p=0.03), while diet composition and absolute total daily energy expenditure (TDEE) were not different between the two ethnic groups (AA: 2590±77 vs W: 2711±56 kcal/d, p=0.21). However, after correction for individual differences in body composition, TDEE was significantly lower in AA women (−231±74kcal/d, p=0.003). Similarly, energy expenditure during sleep was comparable between ethnicities in absolute terms (p=0.77), but lower in AA women after adjustment for body composition (−81±37kcal/d, p=0.03). Physical activity was not significantly different between AA and white women as assessed by calorimetrically data or by accelerometry (eg. time spent in activity, average intensity of activity (METs), or as #steps). We observed no differences in substrate oxidation (12h and sleeping RQ) or metabolic profile (plasma T3 and T4 concentrations, urinary epinephrine and norepinephrine excretion).ConclusionsEarly in pregnancy, African‐American and White women with obesity have similar energy intake and physical activity but energy expenditure per kg of metabolic mass is significantly lower in women who are African‐American. Energy requirements used by clinicians to counsel pregnant women on healthy weight gain are not race‐specific. The lower energy expenditure in African‐American women may therefore lead to unintentional overeating and contribute to the increasing prevalence of excessive gestational weight gain in African‐American women.Support or Funding InformationThis study was funded by the National Institutes of Health (R01DK099175; Redman) and in part by U54GM104940 and P30DK072476.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.