Parents’ Contributions to Childhood Obesity

Although there is a general consensus that preventing obesity in childhood is one key to halting the ever-increasing epidemic of obesity, there is little agreement about how early in life such interventions should begin. A study in the International Journal of Epidemiology (2007;36:104) proposes a mechanism to statistically test the difference in the relative contribution of the size of each parent to a child’s birth weight and rate of weight gain during infancy.

Mother’s weight has more influence

The relative findings of the study are that the height and weight of each parent contributes equally to their child’s weight gain during infancy, but that the child’ birth weight is more influenced by the mother’s weight than by the father’s weight. The proportion of the variance in birth weight or infant weight gain explained by parent size is very small, and birth weight and infant weight gain, in turn, explain only a small proportion of the variability in later weight.

A second study tests the fetal over-nutrition hypothesis

The fetal over-nutrition hypothesis proposes that increased obesity throughout a person’s lifetime can be traced back to obesity and overweight in his or her mother. Dr. Debbie A. Lawlor and colleagues at the University of Bristol, UK, and the University of Queensland, Australia, evaluated the associations between parents’ prepregnancy body mass indexes (BMI, kg/m2) based on height and weight reported by the mother at her first antenatal clinic visit and on the offspring’s BMI (height and weight measured at age 14). The study included 3,340 parent-offspring trios from a birth clinic in Brisbane (Am J Epidemiol. 2007;165:418)

Once again, the relation to the mother’s weight was strongest

The maternal-offspring BMI association was stronger than the paternal-offspring BMI association, according to the authors. Additional adjustment of these results for the child’s report of eating fast food and exercising did not change any of the association, nor did adjusting for maternal exercise during pregnancy and family diet at age 14. The authors note that their method for evaluating the effects of lifestyle on weight were not exact and more detailed physiologic studies are needed to establish the exact mechanisms that result in the maternal effect upon the offspring’s weight. They also point out that while BMI is easy to assess, it cannot differentiate between lean mass and fat mass.

Some thoughts to ponder

In an editorial in the International Journal of Epidemiology (2007;36:104), Dr. Robert C. Whitaker, of Mathematica Policy Research, Princeton, NJ, commented on the possibility that obesity can be traced back to an obese mother. He writes, “Parents in many countries now face the challenge of rearing their children to have a healthy weight and body image in an environment that fights against both. Epidemiological research that assigns a relative contribution of each parent to a child’s weight poses the risk that some might use this information to split parents over an issue on which they need to be united in support of their child. Many of the collective decisions our society has made to advance itself, from how we build our neighborhoods to how we transport ourselves to how we obtain our food, appear to have contributed to harm we never intendedthe obesity epidemic.”