Food and the Family: Weighing the Power of Culinary Nagging
By Bryan Caplan
Parents habitually try to influence what their kids eat. “Eat up.” “Clean your plate.” “No dessert until you finish your vegetables.” “Soda? No, you get milk.” At least in the modern U.S., parents’ main goals seem to be to (a) Increase the total amount of food kids eat, and (b) Increase the healthiness of the food they do eat.
Does all this nagging actually work? You can’t answer this question just by correlating parents’ nagging with childrens’ eating. As usual, we have to consider the possibility that the cause of the correlation is partially or entirely genetic. Maybe health-conscious parents sire health-conscious kids, and the nagging is just a lot of hot air.
What do the data say? The best paper I tracked down was John Hewitt’s “The Genetics of Obesity” (1997, Behavior Genetics 27). It’s got very strong results: Nature can account for all of the family resembance in the Body Mass Index; nurture doesn’t matter at all:
None of the reported twin studies found shared family environmental variation to be significant, while only one out of four large-scale adoption studies found significant evidence for some small influence of measured shared environments (Price et al, 1987). The absence of much, if any, shared family environmental influence may be unsurprising in studies of adults who have long since left their childhood home, but it appears to be true even for 11-year-old twins (Bodurtha et al., 1990) or adopted children studied from birth to age 9 years (Cardon, 1994, 1995).
I suspect many people – and most parents – will be incredulous. How can all their effort add up to nothing? Hewitt’s got a lucid explanation:
[E]vidently what the family has on its table must be less important than what individuals take up from the table or leave behind, what is available in the refrigerator must be less important than how often it is sampled and how much individuals take out, and what is provided in the household is secondary in importance to consumption decisions of the individual. Evidence for the heritability of individual differences in food consumption has been reported by de Castro (1993), who found substantial genetic but no shared environmental influences on total energy intake as well as meal frequency and meal size.
As usual, a zero shared environmental effect doesn’t show that parents can’t change what their kids eat. It just shows that variations within the observed range don’t matter. If all parents nag, then a total cessation of nagging might matter. Nevertheless, the data do show that parents might as well sharply reduce their nagging. If you’re at the 90th percentile of the distribution of food policing effort, you might as well drop down to the 10th percentile. Your life will be easier, family meals will be more pleasant, and on average, your kid’s weight will stay the same.
You might object: Hewitt only measures weight, not healthiness – and it’s a lot easier to influence the quality of your kids’ food than the quantity. That’s plausible for young kids. In the long-run, though, your kids grow up, and eat what they like. “Maybe I’ll have instilled good habits by then,” you say? Yeah, maybe. But what makes you so sure that your kid won’t do the opposite just to spite you?
The bottom line for parents, as usual, is: Chill out. Your kid will probably do fine whatever you do. And even if he does badly, your parenting is unlikely to help.