In women with obesity, excess gestational weight gain (≥270 g/week) occurs in 2 out of 3 pregnancies and contributes to metabolic impairments in both mother and baby. To improve obstetrical care, objectively assessed information on energy balance is urgently needed. The objective of this study was to characterize determinants of gestational weight gain in women with obesity.

This was a prospective, observational study of pregnant women with obesity. The primary outcome was energy intake calculated by the energy intake-balance method. Energy expenditure was measured by doubly labeled water and whole-room indirect calorimetry and body composition as a 3-compartment model by air displacement plethysmography and isotope dilution in early (13–16 weeks) and late (35–37 weeks) pregnancy.

In pregnant women with obesity (n = 54), recommended weight gain (n = 8, 15%) during the second and third trimesters was achieved when energy intake was 125 ± 52 kcal/d less than energy expenditure. In contrast, women with excess weight gain (67%) consumed 186 ± 29 kcal/d more than they expended (P < 0.001). Energy balance affected maternal adiposity (recommended: –2.5 ± 0.8 kg fat mass; excess: +2.2 ± 0.5; inadequate: –4.5 ± 0.5; P < 0.001) but not fetal growth. Weight gain was not related to demographics, activity, metabolic biomarkers, or diet quality. We estimated that energy intake requirements for recommended weight gain during the second and third trimesters were not increased as compared with energy requirements early in pregnancy (34 ± 53 kcal/d, P = 0.83).

We here provide what we believe are the first evidence-based recommendations for energy intake in pregnant women with obesity. Contrary to current recommendations, energy intake should not exceed energy expenditure.

ClinicalTrials.gov, NCT01954342.

This study was funded by the National Institutes of Health (R01DK099175) and the Clinical Research Cores at Pennington Biomedical Research Center (U54GM104940 and P30DK072476).