Do Women Lose Weight While Breastfeeding?

Michael Chitty · January 19, 2021
Is it true that women lose weight when they're breastfeeding? Is there any scientific evidence that addresses this issue?

It’s commonly believed that women lose weight while breastfeeding. So far, science has been able to demonstrate many health benefits for mother and baby associated with breastfeeding. However, its role in postpartum maternal weight control isn’t so clear.

There’s always talk of the benefits of breastfeeding for a mother. But does the mother benefit equally if she breastfeeds for a month or a year?

Benefits of breastfeeding

Breastfeeding is an important public health issue. Children who breastfeed are known to be protected against infection and sudden infant death syndrome. They also have a lower risk of chronic diseases, including obesity.

On the other hand, experts have shown that mothers who breastfeed have a lower risk of type 2 diabetes, hypertension, and ovarian and breast cancers. However, the effects of breastfeeding on the mother’s weight in the short or long term aren’t so clear.

Energy cost of breastfeeding

Experts estimate that exclusive breastfeeding requires a daily energy expenditure of approximately 500 kilocalories. Therefore, compared to women who aren’t breastfeeding, those who do breastfeed may have an advantage in terms of postpartum weight loss.

Do Women Lose Weight While Breastfeeding?

Two studies that examined breastfeeding and its association with maternal weight more than 2 years after birth are noteworthy. The first was in Norwegian women with a follow-up for 3 years after delivery. They classified the mothers according to whether they were fully or partially breastfeeding, or not breastfeeding at all.

Only mothers who fully breastfed up to 6 months showed a statistically significant decrease in weight. The definition of fully breastfeeding referred to feeding exclusively breast milk – never infant formula, other milk, or semi-solid or solid foods.

In the second case, very long-term Finnish mothers were studied. Mothers were assessed for weight after 16-20 years from their last pregnancy. The analyses were made from data provided by the mothers, but also from their medical records.

The researchers found an association between weight, at the time of the study, with weight before pregnancy and with an average duration of breastfeeding. The study concluded that only mothers with prolonged breastfeeding (more than 10 months) returned to their pre-pregnancy weight. This was seen over the course of the 20 years of the study.

Do Women Lose Weight While Breastfeeding?

Additionally, the data revealed that, although there was a gradual weight gain over time in all groups, the difference between the groups remained the same.

Thus, after almost 2 decades of having their children, mothers with a short duration of breastfeeding gained significantly more body weight (14 kilograms) than mothers in the medium (8.3 kilograms) or long (7.6 kilograms) duration of breastfeeding groups.

At shorter durations, does a woman lose weight while breastfeeding?

In periods from 6 to 24 months after birth, a systematic review that polled 646 articles published on this topic stands out. The authors identified only 15 studies that met their inclusion criteria.

We should note here that, out of these 15 studies, only five were of a high enough methodological quality. Out of these five studies, four of them found a significant association between the duration of exclusive breastfeeding and maternal weight loss.

However, when they analyzed the 15 studies together, the association isn’t visible. The authors concluded that the considerable heterogeneity among the studies prevented their pooling. So far, then, there’s insufficient evidence to support an association between breastfeeding and maternal weight loss.

In general, establishing a cause-and-effect relationship of public health phenomena isn’t so easy in science. We would require different studies in order to produce similar results after analyzing defined population samples.

Therefore, our conclusion is that demonstrating that women lose weight while breastfeeding still needs more thorough research.