The most incisive guide to issues facing the American family today . . . An invaluable resource for anyone wishing to stay on the cutting edge of research on family trends.

-W. Bradford Wilcox
Associate Professor of Sociology, University of Virginia 

The Roots of Obesity

Bryce J. Christensen and Robert W. Patterson

The media regularly report on the alarming rise of childhood obesity in the United States. Unfortunately—but predictably—these reports rarely mention family disintegration as a cause of the epidemic. Now a new study by researchers at the Children’s Hospital of Los Angeles has shown that the retreat from family life fosters childhood obesity in two ways—not only by cutting children’s ties to their father (as other studies have concluded), but also by denying them the companionship of siblings.

The researchers determined the home environments most likely to foster obesity by drawing on data collected from 17,565 children included in a nationally representative sample of children who entered kindergarten in 1998–99, comprising students in public and private schools and in both full-day and part-day programs. This database includes survey data for these students in kindergarten as well as the third and fifth grades.

Statistical analysis of the data established that “family structure was significantly associated with the obesity rate.” In each grade, children from single-mother families had higher rates of obesity than children from two-parent families (p = 0.05 in kindergarten; p = 0.03 in third grade; p = 0.003 in fifth grade). When the researchers re-examined their data in a more sophisticated model that took into account background characteristics such as race, household income, and maternal education, the tie between family structure and obesity fell below the threshold of statistical significance for kindergarten and the third grade. However, even in this sophisticated model, the tie between family structure and childhood obesity remained significant for the fifth grade (p = 0.05).

Further analysis revealed that it is not just the absence of a father that tends to make children obese; the absence of siblings also fosters obesity. “In every grade,” the researchers report, “we found that children with no siblings had higher BMI [Body Mass Index] and a higher probability of being obese than children with siblings.”

Combining their two findings, the researchers interpret their analysis as “strong evidence that children who lived with a single mother and especially children who had no siblings were at the greatest risk for childhood obesity.”

The researchers speculate that the children of single mothers are particularly likely to grow fat because “single mothers are likely to have fewer resources [than married mothers], including lower availability of time and social supports, to regularly provide homemade meals for themselves and their children. Similarly, single mothers may lack the time or energy to play actively with their children and to encourage physical activities.”

While they acknowledge that many social scientists believe that “additional children in the family may dilute available parental time and resources,” the researchers suggest, “Siblings may also serve as a stimulus for child-to-child interactions, cooperative play, or activities that increase the time each child devotes to physical activity. Older siblings may even serve as role models or share the caretaking role with parents.”

No doubt the nation’s editorialists will continue to bewail the upsurge in childhood obesity. But those editorialist will do little to help combat that upsurge until they take a hard look at the American retreat from marriage and childbearing.

(Alex Y. Chen and José J. Escarce, “Family Structure and Childhood Obesity, Early Childhood Longitudinal Study—Kindergarten Cohort,” Preventing Chronic Disease 7.3 [May 2010]: A50.)