Effects of Breastfeeding Promotion Intervention and Dietary Treatment in Postpartum Women with Overweight and Obesity: Results from a Randomized Controlled Trial on Weight and Cardiometabolic Risk Factors.

Background: Childbearing increases the risk of weight gain and cardiometabolic disease. The reset hypothesis suggests that lactation has protective cardiometabolic effects on the mother. The hypothesis is based on observational studies, and the possible interacting role of weight loss needs to be elucidated.

Objectives: This study aimed to examine the individual and interaction effects of a breastfeeding promotion intervention (BPI) and dietary intervention for weight loss postpartum (Diet) on body weight and cardiometabolic risk factors at 6 mo postpartum.

Methods: Pregnant women (n = 156) with a prepregnancy BMI of 25 to 35 kg/m were randomized to 4 groups in a 2 × 2 factorial design: BPI, Diet, both treatments, or no treatment. BPI consisted of individual counseling by a lactation consultant during pregnancy, at childbirth, and monthly thereafter or more frequently based on individual needs. Diet was initiated at 11 wk postpartum. Body weight, body composition, waist and hip circumferences, markers of lipid and glucose metabolism, and blood pressure were measured at 2 wk and 6 mo postpartum. We analyzed main and interaction effects using 2-way analysis of covariance adjusted for baseline values.

Results: Among the participants attending both visits (n = 108), 99% practiced any breastfeeding at baseline and 97% at follow-up. The BPI did not affect rates of exclusive or partial breastfeeding, age at introduction of complementary foods, or have main effects on body weight or cardiometabolic risk factors. There was a main effect of Diet reducing body weight, fat mass, fat-free mass, percentage fat mass, waist and hip circumferences, fasting glucose, and insulin (all P ≤ 0.03), with no interactions between the treatments.

Conclusions: There were no effects of BPI on body weight or cardiometabolic risk factors at 6 mo postpartum. Diet caused weight loss and had favorable effects on risk factors for cardiovascular disease and type 2 diabetes. This study was registered at clinicaltrials.gov as NCT03580057.