3 Factors Obscure Breastfeeding’s Effect on Obesity

Breastfeeding has important, indisputable, and immediate benefits for an infant’s health. Protection from infectious, gastrointestinal, and allergic diseases are at the top of the list. Perhaps because of these important short-term benefits, many authorities promote some long-term benefits for breastfeeding that are not so well proven.

Obesity is often cited. For example, CDC states in its publications that breastfeeding for nine months reduces an infant’s risk of becoming overweight by more than 30%.

But the most recent World Health Organization (WHO) analysis of the evidence base contradicts CDC’s claim. The analysis finds that the best studies show a possible — but disputable — small reduction in excess weight for children with longer durations of breastfeeding. In other words, the data is too shaky to prove or disprove an effect. Here are three reasons why:

1. A small effect size. The WHO analysis found that the best studies show that any effect on excess weight is likely to be small — about 10%. Such a small effect is difficult to prove or disprove.
    
2. Publication bias. Smaller studies have tended to show a bigger effect, creating a significant problem with publication bias. When publication bias is taken into account, we are left with a much smaller effect than the 30% reduction that CDC is advertising.
    
3. Confounding variables. Most studies of breastfeeding showing a reduction in excess weight were conducted in developed countries. Duration of breastfeeding in those countries is associated with higher education and income levels, which in turn are associated with lower rates of excess weight. So the WHO analysis concludes that we cannot rule out these confounding factors as the explanation for the observed effect.

 
The immediate benefits of breastfeeding are more than enough to persuade mothers. Inflated claims only cloud the picture.

“Exaggeration is truth that has lost its temper” — Khalil Gibran

Click here to view an outstanding seminar at UAB by Ronald Kleinman on this subject and click here for the WHO analysis of the long-term effects of breastfeeding.

My Sweet Baby, photograph © paxye / flickr

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