Association between Breastfeeding, Maternal Weight Loss and Body Composition at 3 Months Postpartum

Abstract

Background

Pregnancy results in substantial increases in maternal body weight that may persist through postpartum. Weight gained during pregnancy and retained postpartum has been previously shown to contribute to obesity in women of childbearing age. It is often suggested that breastfeeding (BF) is an efficient means of promoting postpartum weight loss (PPWL) and favorable changes in body composition (reduction in body fat). However, the influence lactation has on short term changes in body weight and body composition have not been well-described in contemporary women.

Objective

To explore the relationships between BF practices, PPWL, and % body fat at 3 months postpartum.

Methods

Fifty women (32.6 ± 4.1 years; 3.2 ± 0.2 months postpartum) reported their pre-pregnancy weight and highest weight during pregnancy. Height, current weight, and % body fat (dual energy x-ray absorptiometry) were measured. Women were categorized as any BF or non-BF. For those who breast-fed, their BF practices (number of feeds/day; total time feeding [min/day]; milk volume expressed [ml/day]; energy cost of lactation [kcal/day]) were estimated using a combination of infant test weighing (1 day) and a 3-day BF diary. The PPWL was calculated as absolute (kg) and proportional (%) change from highest weight in pregnancy after subtracting baby birth weight. Differences in PPWL and % body fat between BF and non-BF were assessed by independent t-tests. Associations between BF practices, PPWL, and % body fat were assessed using Pearson correlation coefficients. Logistic regression was used to evaluate associations between BF and PPWL and % body fat; pre-pregnancy BMI was included in the models for these analyses as it significantly correlated with PPWL. For all analyses statistical significance was set as p<0.05.

Results

The BF group (n=39) did not differ from non-BF (n=11) for absolute PPWL (7.3 ± 3.7 vs. 5.0 ± 3.4kg), % PPWL (9.3 ± 4.8 vs 5.9 ± 4.3 %) and % body fat (37.6 ± 8.0% vs. 43.3 ± 6.9%) respectively. The BF women fed babies 9 ± 3 feeds/day for a total of 161 ± 74 min/day. Milk volume expressed was 738 ± 245 ml/day for an estimated energy cost of lactation of 653 ± 215 kcal/day. Absolute PPWL, % PPWL and % total body fat were not associated with any breastfeeding practices. In regression models, pre-pregnancy BMI was significantly associated with PPWL (β = −0.4, p= 0.001) and % body fat (β = 1.1, p < 0.001) although BF was not. Having a higher pre-pregnancy BMI was associated with less PPWL and higher % body fat at 3 months postpartum.

Conclusions

At 3 months postpartum, BF appears to have little association with PPWL or % body fat, while pre-pregnancy BMI is significantly associated with both. This reinforces the idea that having a BMI in a healthy range prior to pregnancy may be important for postpartum weight management. Detailed assessment of factors affecting energy balance including intake and components of energy expenditure beyond 3 months are critical to understanding trajectories of weight and body composition change postpartum

Support or Funding Information

The ENRICH Program is funded through the Alberta Innovates - Health Solutions, Collaborative Research and Innovation Opportunity (CRIO) team grant.