Can new mums shed their baby weight through breastfeeding?

Breastfeeding mothers in Singapore appear to have an edge over those who feed their newborns formula in terms of shedding some baby weight, according to a study.

Data from 332 first-time mothers (mean age 31.2 years, 79.8 percent Chinese, mean prepregnancy BMI 22.5 kg/m²) showed that around one-third of these women had substantial postpartum weight retention (PPWR), defined as retaining at least 5 kg of body weight, at 6 months (35 percent) and 12 months (31 percent) postpartum. Women who practiced exclusive breastfeeding retained less weight than those who practiced mixed breast- and formula feeding or exclusive formula feeding both at 6 months (mean PPWR: 7.26, 9.08, and 8.21 kg, respectively) and 12 months (mean PPWR: 7.43, 8.67, and 8.33 kg, respectively). [Nutrients 2024;16:2172]

Compared with exclusive breastfeeding, exclusive formula feeding was associated with a more than twofold increased risk of substantial PPWR at 6 months (risk ratio [RR], 2.11, 95 percent confidence interval [CI], 1.32–3.28). A slightly less risk increase was observed for mixed breast- and formula feeding (RR, 1.85, 95 percent CI, 1.15–2.99).

The risk estimates were attenuated at 12 months, with mixed feeding and exclusive formula feeding correlating with 46-percent (95 percent CI, 0.89–2.39) and 88-percent (95 percent CI, 1.16–3.04) higher risks of substantial PPWR at 12 months, respectively.

In subgroup analyses of women who practiced mixed or exclusive formula feeding prepregnancy, overweight or obesity influenced how much weight they retained, such that those with prepregnancy BMI of ≥23 vs <23 kg/m² had greater PPWR.

“Our findings confirm a positive association between mixed or exclusive formula feeding at 6 months and increased PPWR up to 12 months. This aligns with results from a meta-analysis of cohort studies, which showed that breastfeeding for at least 6 months reduced PPWR until at least 48 weeks postpartum,” the investigators said. [Clin Nutr 2018;37:1224-1231]

In addition, “exclusive formula feeding had a more pronounced negative impact on PPWR than mixed feeding, indicating that any level of breastfeeding helps mitigate PPWR, with the most significant benefits arising from exclusive breastfeeding,” which is consistent with findings from large cohorts in Taiwan and Japan, they continued. [Nutrients 2020, 12, 1065; PLoS ONE 2022;17:e0268046]

Why formula feeding might be linked to more PPWR can be attributed to the absence of metabolic benefits from breastfeeding. According to the investigators, breastfeeding helps mums burn more calories and release stored fat. [Curr Opin Clin Nutr Metab Care 2019;22:413-417]

As such, national strategies to enhance postnatal care services are critically needed, they stated. Targeted lifestyle interventions that focus on changing eating habits, along with proactive breastfeeding support, can be especially helpful for mums, especially in the first 2 years after giving birth, which the investigators referred as an optimal intervention window for returning to prepregnancy BMI levels. [Sci Rep 2023;13:4834; Nutrients 2023;15:2075]

“Implementing effective lifestyle modifications is pivotal not only for mitigating PPWR but also for improving subsequent perinatal outcomes and enhancing long-term health in women,” the investigators said.