Systematic review and meta-analysis of breastfeeding and later overweight or obesity expands on previous study for World Health Organization

Aim To update a systematic review and meta-analysis of the association of breastfeeding with overweight or obesity that had been commissioned by the World Health Organization. We also assessed the likelihood of residual confounding. Methods Two independent reviewers searched MEDLINE, LILACS and Web of Science for manuscripts published between August 2014 and May 2021. Studies that only evaluated infants were excluded. Random-effects models were used to pool the estimates. Results The review comprised 159 studies with 169 estimates on the association of breastfeeding with overweight or obesity, and most of the studies were carried out among individuals aged 1-9 years (n = 130). Breastfeeding protected against overweight or obesity (pooled odds ratio:0.73, 95% confidence interval:0.71; 0.76). And, even among the 19 studies that were less susceptible to publication bias, residual confounding and misclassification, a benefit was observed (pooled odds ratio:0.85, 95% confidence interval:0.77; 0.93). Among those studies that were clearly susceptible to positive confounding by socioeconomic status, a benefit of breastfeeding was observed even after adjusting for socioeconomic status (pooled odds ratio:0.76, 95% confidence interval: 0.69; 0.83). Conclusion Breastfeeding reduced the odds of overweight or obesity, and this association was unlikely to be due to publication bias and residual confounding.