Background

In women with obesity, excess gestational weight gain (≥270 g/week) occurs in two out of three pregnancies and contributes to chronic metabolic impairments in both mother and baby. To improve obstetrical care of patients with obesity, objectively assessed information on energy intake and/or energy expenditure, the chief determinants of weight gain is urgently needed.

Methods

In a prospective observational cohort study, women with obesity (BMI≥30 kg/m2, ≤15 weeks of gestation) expecting a singleton pregnancy completed energy balance measurements from 13-16 to 35-37 weeks gestation. The primary outcome was energy intake throughout the second and third trimester measured by the intake-balance method where energy expenditure measured by doubly-labeled water was summed with changes in body composition (3-compartment model).

Results

Recommended, excess and inadequate weight gain was observed in 8 (15%), 36 (67%), and 10 (19%) women, respectively. Energy balance or the difference between energy intake and energy expenditure, determined gestational weight gain (P<0.0001). Recommended weight gain was achieved when energy intake was 125±52 kcal/d less than energy expenditure whereas women with excess gestational weight gain consumed 186±29 kcal/d more than they expended (P<0.001). Energy balance affected adiposity changes (recommended: -2.5±0.8 kg fat mass, excess: +2.2±0.5, inadequate: -4.5±0.5 kg, P<0.001), but not fetal growth. Weight gain was not related to demographic characteristics, physical activity, metabolic biomarkers, or diet quality.

Conclusions

We here provide the first evidence-based recommendations for energy intake in pregnant women with obesity. Contrary to current recommendations, women with obesity should not consume additional calories to achieve healthy weight gain in pregnancy.Funding: This study was funded by the National Institutes of Health (R01DK099175)