Recommendations for energy intake and weight gain for pregnant women with obesity

Clinical Question What are the recommendations for energy intake and weight gain for pregnant women with obesity? Recommendations Recommendation 1: In pregnancies of obese individuals, second/third trimester energy intake should not exceed energy expenditure; thus, additional calories should be avoided to optimize gestational weight management and reduce maternal fat accumulation (Evidence quality: Very low [D], Recommendation strength: Weak). Recommendation 2: Gestational weight gain (GWG) below the Institute of Medicine (IOM) limit or weight loss might be safe and beneficial for pregnant women with obesity [Evidence quality: Moderate (B), Recommendation strength: Strong], especially for those with (body mass index [BMI] ≥40.0 kg/m2) obesity [Evidence quality: Low (C), Recommendation strength: Strong]. Recommendation Explanation Energy intake for pregnant women with obesity Energy intake during pregnancy is positively correlated with GWG, but overweight and obese pregnant women require less fat accumulation. Research has demonstrated a significant positive correlation between energy intake and GWG, although energy requirements vary among women with different BMIs; Overweight and obese women require less fat accumulation, whereas underweight women need greater fat reserves. A systematic review revealed that the association between macronutrients (protein, fat, and carbohydrates) and GWG remains inconclusive.[1] While fat type (e.g., saturated fat) may influence GWG, the roles of protein and carbohydrates warrant further investigation. Notably, obese pregnant women present unique metabolic characteristics—their actual energy expenditure is significantly lower than traditional model predictions, primarily because of reduced physical activity levels and metabolic heterogeneity (e.g., insulin resistance and variations in thyroid hormone levels), which further impact energy expenditure.[2] Current energy requirement models are limited by inadequate representation of obese women and those in minority groups and insufficient consideration of weight gain and metabolic rate changes.[3] Therefore, addressing the individualized needs of pregnant women across BMI categories is crucial for achieving scientific and precise gestational weight management. Excessive energy intake should be avoided in overweight and obese pregnant women. According to the 2009 IOM guidelines, women entering pregnancy with obesity should limit their total weight gain to 5–9 kg. Despite these recommendations, excess gestational weight gain occurs in 2 out of every 3 pregnancies among women with obesity, increasing the risks of obesity and type 2 diabetes mellitus in both the mother and the baby. The IOM recommends that all pregnant women increase energy intake by 340–450 kcal/d during the second and third trimesters. Such recommendations for dietary energy intake were based on studies in pregnant women without obesity. Some studies have raised concerns that this recommendation might increase the risk of gestational diabetes, preeclampsia, and excess postpartum weight retention in obese pregnant women, and there is a lack of differentiated recommendations for women with varying degrees of obesity. In recognition of the different needs of patients with obesity, the American College of Obstetricians and Gynecologists (ACOG) states that pregnant women with obesity may need fewer extra calories but does not provide specific guidance. Energy intake recommendations for pregnant women with obesity are therefore either extrapolated from women without obesity or based on subjective measures, rather than on appropriate evidence. Thus, for women with obesity, effective weight gain management during pregnancy is an unmet need in clinical practice. To improve obstetrical care, objectively assessed information on energy balance is urgently needed. A 2019 study employing gold-standard methods (doubly labeled water and indirect calorimetry) evaluated gestational weight management in 54 obese pregnant women and revealed that 67% exceeded the weight gain recommendations set by the IOM guidelines, with energy intake significantly correlated with weight gain.[4] This study revealed that obese pregnant women, due to their higher metabolic efficiency (conversion of fat to lean mass), may meet pregnancy requirements without additional caloric intake, suggesting that current IOM recommendations are likely excessive. Furthermore, dietary interventions (e.g., energy restriction) significantly reduced GWG and postpartum weight retention, with healthy dietary interventions alone proving more effective than physical activity alone, particularly when combined with calorie and macronutrient targets.[5] Personalized weight gain goals based on obesity class (e.g., maintaining prepregnancy weight for class 3 obesity [BMI ≥40.0 kg/m2]) were shown to be more feasible, although a balance between energy restriction and fetal nutritional needs must be achieved to ensure maternal and fetal health.[6] A prospective observational study of pregnant women with obesity revealed that recommended weight gain during the second and third trimesters was achieved when energy intake was 125 ± 52 kcal/d less than energy expenditure and indicated that energy intake requirements for achieving recommended weight gain during the second and third trimesters were not increased compared with energy requirements early in pregnancy (34 ± 53 kcal/d, P = 0.83).[7] The results suggested that pregnant women with obesity should not consume additional energy when pregnant. The energy requirement for fetal development was met through the mobilization of maternal fat mass, with no adverse effects observed in maternal or fetal outcomes. This study provided evidence-based recommendations for energy intake in pregnant women with obesity, which indicated that energy intake should not exceed energy expenditure for pregnant women with obesity. The safety of weight gain below the IOM recommendation for pregnant women with obesity. In 2024, Kari Johansson et al.[8] used the data of 15,760 singleton pregnancies among obese women from the Stockholm–Gotland Perinatal Cohort to evaluate the safety of GWG below the IOM recommendation or weight loss in obese women. In women with class 1 obesity (BMI 30.0–34.9 kg/m2) or class 2 obesity (BMI 35.0–39.9 kg/m2), GWG below the recommendation (5 kg) or weight loss was not related to an increased risk of adverse composite outcomes. In women with class 3 obesity (BMI ≥40.0 kg/m2), GWG below the IOM recommendation or weight loss was associated with a reduced risk of adverse composite outcomes. This high-quality study suggests that GWG below the lower limit of the IOM recommendation is likely safe for pregnant women with obesity and might be beneficial for those with class 3 obesity. Although the IOM concluded that low weight gain or weight loss in women with obesity “may be associated with a more favorable trade-off among outcomes”, concerns about the potential for increased risks of fetal growth restriction and ketonemia (and possible related neurocognitive deficits in childhood) prohibited the IOM review committee from recommending weight gain below 5 kg. New research on energy balance during pregnancy has since shown that women with a BMI of 30.0 kg/m2 or higher can mobilize energy from fat mass to compensate for the increased energy demand for the products of conception. In addition, although studies have concluded that weight loss increases the risk of small-for-gestational-age births for pregnant people with class 1 or 2 obesity, the results are inconsistent for those with class 3 obesity. However, small-for-gestational-age birth is a statistical definition that does not necessarily imply pathology; 50–70% of small-for-gestational-age births are estimated to be constitutionally small but healthy. Thus, it is unclear whether this outcome is sufficiently serious to outweigh the many adverse maternal outcomes that are associated with weight gain. Therefore, it is necessary to critically reevaluate the GWG recommendations for women with obesity, particularly those with class 3 obesity, and develop separate guidelines on the basis of the severity of obesity. Weight gain lower than the IOM recommendation or weight loss in pregnancies of women with class 1, 2, and 3 obesity could help to reduce the risks of maternal and offspring complications.[8] Trials, observational studies, and meta-analysis examining low amounts of gestational weight gain in different obesity classes have included a small number of short-term perinatal outcomes, providing incomplete evidence to inform guidelines. However, evidence on how gestational weight gain is linked with longer-term maternal health outcomes is scarce. Therefore, high-quality studies with large sample sizes evaluating long-term outcomes are needed in the future. During pregnancy, monitoring fetal growth is important to ensure healthy development; the mother should also be monitored for the presence of ketones and ensure adequate intake of high-quality protein. Evidence Summary This rapid recommendation was developed in accordance with the standardized methodology framework outlined in the STAR Recommendations.[9] The detailed procedures are available in the Supplementary Materials, https://links.lww.com/CM9/C716. Funding This work was supported by grants from the Noncommunicable Chronic Diseases-National Science and Technology Major Project (No. 2024ZD0532100), the National Natural Science Foundation of China (No. 82470863), and the Beijing Nova Program (No. 2024010). Conflicts of Interest None.