Breast Is Best, But Does It Prevent Obesity?
The World Health Organization is doing some great work on obesity in the European Region. For instance, they just published an outstanding new report at ECO2019 on the prevalence of severe childhood obesity in 21 countries. Unfortunately, though, they buried it in a press release that falsely promotes breastfeeding as a proven effective strategy to prevent obesity in childhood.
While it may be true that “breast is best,” two other things are clear. One, all we have is a correlation between breastfeeding and less childhood obesity. And two, if it does have an effect, it’s relatively small.
Beating a Correlation to Death
No matter how many times you repeat the observation of a correlation, it doesn’t prove causation. It simply builds up a bias of familiarity.
The paper that WHO just published about breastfeeding in Obesity Facts notes this fact quite clearly:
The data come from cross-sectional studies, which can detect an association between exposure and outcome but do not justify causal inference. Furthermore, although many variables were used to adjust the models, it is impossible to rule out residual confounding by other unmeasured or unmeasurable confounders.
And yet, the authors contradict themselves in their conclusions:
The present work confirms the beneficial effect of breastfeeding against obesity.
These claims of a proven benefit are simply untrue and the authors said so themselves. What’s more, WHO’s own systematic review on this subject makes it clear that residual confounding is a problem. Publication bias on this subject is another problem. And further, the review says any effect is likely to be small (~10%) if it exists at all.
Writing in Current Obesity Reports, Jessica Woo and Lisa Martin are even more direct:
The concept of promotion of breastfeeding as a front-line strategy for the primordial prevention of obesity is not supported by the literature.
Exaggeration Begets a Backlash
Exaggerated claims are dangerous because they undermine trust. And trust is essential for promoting public health. In the absence of trust, misinformation proliferates. Truth becomes devalued.
While there’s little doubt that breastfeeding is ideal, some mothers feel a great sense of failure when they find it’s not working for them. One result is a backlash against dogmatic breastfeeding promotions. Wise public health advocates will be careful.
Prevention That Really Works
Does breastfeeding prevent obesity? Maybe. A little bit. Or maybe not.
Preventing obesity is important. And yet, despite all best efforts, obesity rates have been growing now for three decades. So we must work harder to separate facts from speculation and fiction.
We need prevention strategies that really, really work.
Click here for the WHO study and here for its press release.
Nursing on the Isle of Man, photograph © Khaotikit / flickr
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May 1, 2019
