Breastfeeding for Three Months or More Linked to Lower Long-Term Weight Gain in Women

Key Takeaways: 

• Women who breastfeed for at least three months may gain significantly less weight later in life, with differences observed decades after childbirth.
  
• The strongest long-term effect is seen in women who had overweight or obesity before pregnancy.
  
• Breastfeeding appears to influence energy balance, although individual responses vary and support remains essential.
  
  
  

Long-term impact of breastfeeding on weight

Breastfeeding has long been associated with short-term postpartum weight changes, but new research suggests its effects may extend much further. A study conducted by researchers at the University of Oslo indicates that women who breastfeed for at least three months may experience lower weight gain even decades later.

According to the findings, women gained up to 6.5 kilograms less on average later in life if they breastfed for a minimum of three months. This extends the understanding of breastfeeding beyond its immediate postpartum benefits, highlighting its potential role in long-term weight trajectories.

Previous research has largely focused on weight changes in the first one to two years after childbirth. In contrast, this study followed women for up to 50 years after they had stopped breastfeeding, offering a rare insight into lifelong health patterns. The findings are expected to inform further research into maternal cardiovascular risk.

Large-scale study provides robust data

The analysis drew on data from the Women and Health Study, which includes more than 170,000 women in Norway. The results were published in the American Journal of Clinical Nutrition. 

This large cohort allowed researchers to examine how breastfeeding duration relates to weight development across different groups of women, while accounting for factors such as education, physical activity, and smoking.

Strongest effect seen in women with overweight

The most pronounced differences were observed among women who had overweight or obesity in early adulthood, prior to pregnancy.

“We compared women in this group who were otherwise similar in terms of education level, physical activity and smoking. We then found that those who breastfed for three to 15 months gained on average up to 6.5 kilos less from young adulthood to middle age, compared with those who breastfed little,” says Thorbjørn Brun Skammelsrud.

Skammelsrud is completing his doctoral research at the Department of Nutrition, Institute of Basic Medical Sciences at the University of Oslo.

More modest differences in women with normal weight

Among women who had a normal weight in early adulthood, the long-term effect of breastfeeding was still present but less pronounced. Those who breastfed for three to 15 months gained up to 3 kilograms less compared with those who breastfed for shorter periods.

For women who had been underweight before pregnancy, breastfeeding appeared to have little influence on long-term weight outcomes.

Biological mechanisms and individual variation

The study also highlights the complex relationship between breastfeeding and energy balance.

“Breastfeeding increases energy expenditure, so in theory breastfeeding should contribute to weight loss. But precisely because energy expenditure increases, some women will also experience increased appetite when they are breastfeeding,” Skammelsrud explains.

This means that while breastfeeding may support weight regulation at a population level, individual experiences can differ significantly.

Implications for public health

The study included women who had children as early as the 1940s, although the association between breastfeeding and lower weight was strongest among those who gave birth after 1980. This group is considered more representative of current maternal behaviours, particularly in terms of diet and breastfeeding practices.

In Norway, national guidance generally recommends partial breastfeeding for one year or longer, provided both mother and infant are comfortable. Breastfeeding rates in Norway are relatively high compared with many other countries.

“This is positive for public health. At the same time, the study shows that some women may need extra follow-up after giving birth, particularly those with overweight or obesity,” Skammelsrud says.

Supporting women who choose to breastfeed

The findings reinforce the importance of enabling and supporting breastfeeding where desired.

“In this study, we see that breastfeeding for at least three months has a positive effect on women’s weight later in life. It is therefore important that breastfeeding is facilitated, and that women who wish to breastfeed are offered qualified support,” the researcher says.

Ensuring access to appropriate guidance and support may help maximise both short-term and long-term health outcomes for women.