Breast Feeding and Obesity in Children
Clinical Abstracts
With Comments by Adriane Fugh-Berman, MD
Breast Feeding and Obesity in Children
August 2000; Volume 2; 64
Source: von Kries R, et al. Breast feeding and obesity: Cross-sectional study. BMJ 1999;319:147-150.
Objective: To assess the effect of breast feeding on obesity in children.
Design/Setting/Methods/Subjects: Cross-sectional questionnaire survey of 9,357 children ages five and six of German nationality in Bavaria, southern Germany. This population was a subset of 134,577 children participating in the required school health examination.
Results: The prevalence of obesity in breastfed children was 2.8% while the prevalence of obesity in children who had never been breastfed was 4.5%. A clear dose-response effect was identified. This effect was not explained by differences in social class or lifestyle. After adjustment for confounders, breastfeeding remained significantly protective against development of obesity (odds ratio [OR] 0.75, 95% confidence interval [CI] 0.57-0.98) and being overweight (OR 0.79, CI 0.68-0.93).
In children who had been breastfed for least six months, the risks of being overweight or obese were reduced by 30-40%. Breastfeeding was associated with family makeup and lifestyle, premature births, low birthweight, and early and current diet. More than 10 years of parental education, premature birth, and low birth weight were inversely associated with overweight in childhood; maternal smoking during pregnancy and the child having his or her own bedroom were positively correlated. Full-fat dairy products, sweets, butter, and breakfast cereals were less frequently consumed by overweight children than by normal-weight children.
Funding: Bayrisches Staatsminiitrium fur Arbeit und Sozialordnung, Familie, Frauen und Gesundheit and Stiftung Kindergesundheit.
Comments: This study is intriguing but is not proof of an association; perhaps breastfeeding is a marker for other familial mores that affect the weight of children. The authors are clearly aware of this, and the final logistic regression factored in the independent risk factors of parental education, maternal smoking, low birth weight, own bedroom, and frequent consumption of butter. A higher level of parental education was the only factor that shifted the OR toward unity by at least 10%.
The authors note, rather apologetically, that family income or social class might have been better indicators of socioeconomic status (SES) than parental education, but state that "Unfortunately, in Germany there is no accepted equivalent to the British categories of social class, and respondents to written questionnaires are reluctant to report income." I found that statement amusing because in Britain everyone knows what social class they inhabit; it has been said that in the United States everyone thinks they are middle class. Questions of SES confound much research done in the United States, where we tend to use race as an (inadequate) surrogate for class. In fact, the United States and South Africa are distinct among developed countries in collecting health statistics by race but not class.
Questions of SES confounding aside, this is not the first study to demonstrate an association between breastfeeding and protection from childhood obesity; a dose-dependent reduction in the risk of overweight or obesity has also been observed in a study of breastfeeding in Canadian adolescents born in the 1960s.
What could be a possible mechanism? The authors of the German study point out that one study found higher plasma levels of insulin in bottle-fed infants compared to breastfed infants; it is thought that increased insulin levels may stimulate fat deposition. Alternative Therapies in Women’s Health editorial advisory board member Sadja Greenwood, MD, MPH, suggests that when speculating about why there is less obesity among breastfed babies, could it not be that they work harder to suckle and get less milk/calories than bottle-fed infants, whose parents often overfeed for a variety of reasons?
August 2000; Volume 2; 64Subscribe Now for Access
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