Bryan Caplan  

Food and the Family: Weighing the Power of Culinary Nagging

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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.


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COMMENTS (19 to date)
scott clark writes:

I don't know, I kinda think of the clean your plate mandate as a way to keep your kid from bugging you two hours later because he or she wants to eat again, a little less about wasting food. Its a matter of convinience for the parent. Even after the child would be old enough to go to the 'fridge and get some food for themselves, the child would still be leaving more dishes to do, maybe leaving crumbs, after you've already cleaned the kitchen for the night. Growing up, my father had a
"Kitchen's Closed" policy after it had been cleaned (the policy was never really enforced now that I think about it).

But your point about chilling out still stands.

Zac writes:

I think the nagging has little to do with increasing the total amount or healthiness of what kids eat.. it is more a lesson in manners, ie, teaching a child not to be wasteful or ungrateful. As a child, when I would have friends over and dinner was served, my parents would have a look of horror if a friend didn't finish his baked potato.. and I was scolded by my own parents when they found out I refused to eat squash at my aunt's house. I didn't see it as a big deal, they saw it (and perhaps my aunt saw it) as a slight to my aunt's cooking. One of the only thing my girlfriend's parents like about me is that I am not a "picky eater" - there are few foods I simply dislike - a fact to which my parents credit to themselves with much pride.

My parents were never really worried that I would end up obese (although perhaps they should have, and not bought so much coca-cola and whole milk) but they were genuinely concerned I might grow up to be an ungrateful, picky eater.

Caliban Darklock writes:

Every meal in my house has a defined ritual purpose.

Breakfast: get your own. Prepare it yourself. Don't waste food.

Lunch: select from a parent-provided range of choices. Wait to be served. Don't waste food.

Afternoon snack: optional and on demand once per day between lunch and dinner; select from an open range of choices, restricted only by kitchen inventory. Wait to be served. Don't waste food.

Dinner: dictated by parents. Wait to be served. Don't waste food.

Dessert: only if all dinner eaten. Participate directly in helping serve the entire family. Don't waste food.

These are quite deliberately and consciously representative of the way people encounter food throughout their lives, so the children learn at an early age how to behave in these circumstances. The purpose is more social than dietary for all cases.

Kit writes:

Is "healthy eating" actually healthy? The evidence is remarkably weak. In todays Spiked: Four fat myths about obesity and cancer

"Almost 49,000 American women were followed over an eight-year period in terms of eating, weight, and disease. The women in the intervention group ate ‘healthy’ diets that were low fat and high fibre. The results? There were no statistically significant differences between the intervention and the control group in the incidence of breast cancer, colon cancer, strokes, or heart attacks."

Mass writes:

Bryan, in all your parenting examples, the kids ore obedient and cooperative and the parents have these overly strict and out of date rules.

I'm sure that's the case in many families, but you probably haven't dealt with a really spirited child.

I have a ten year old daughter. I try to be as lenient and lax as possible, but the issue of food is an absolute nightmare.

My daughter snacks 24/7, she is constantly hungry, constantly complaining that we don't have anything to eat (even when we have all her favorite foods fully stocked in the refrigerator, she gets tired of those and wants something new). She'll waste food. For example, she will microwave some food, try a bite, throw the rest out. Then immediately microwave a different kind of food, and repeat four times in the same afternoon. Or when I order take out, she will order three tacos (and would throw an absolute tantrum if I didn't get her full order) and then only eat half of one.

The absolute worst, is making a mess and not cleaning up. I hate being a nag, but I nag constantly about cleaning up, and the place is always a mess. She leaves food *everywhere*. Uneated food, wrappers, dirty plates/utensils everywhere. She is fiercely strong-willed about not cleaning up and it is absolutely exhausting. I don't mind cleaning up some of her mess, but she makes the mess of ten normal kids. She snacks constantly day and night when she's bored and just dirties every clean dish and glass, opens every packaged food item, and throws wrappers and plastics on every floor and in every corner and crevice of the house.

Greg writes:

Doesn't this analysis ignore another confounding factor, culture? Parental influence may not matter much, but people have gotten more overweight overall without, I presume, a significant change in our genetic makeup. So something beyond nature in the nature vs. nurture debate is driving the change. Perhaps it's just like many other factors, where peers and society at large end up having a much greater impact than parents.

david jinkins writes:

Not only does Hewitt's study not measure healthiness, it also doesn't measure eating habits. Maybe nagging/nurture does influence eating habits, only that eating habits aren't correlated with BMI/health. A few observations seem to suggest, at least, that eating habits are influenced by nurture.

First consider that in general people prefer to eat the food they were exposed to growing up. My Turkish wife and I live in Taiwan. I am American. If she misses food, its traditional Turkish cooking (good yogurt, feta, olives). I usually hanker after a good burrito. I think we are fairly typical in this sense. This stylized fact suggests that in some sense peoples' eating habits are influenced by nurture.

Second, consider vegetarians. In my experience, children of vegetarians are more likely to be vegetarian themselves. I am one example. Unless you think that being vegetarian is genetic, this is another example of nurture affecting eating habits.

Jayson Virissimo writes:

"Second, consider vegetarians. In my experience, children of vegetarians are more likely to be vegetarian themselves. I am one example. Unless you think that being vegetarian is genetic, this is another example of nurture affecting eating habits." -David Jinkins

Here is an alternative idea:

(1) Vegetarians tend to have higher IQ scores.

Evidence: http://news.bbc.co.uk/2/hi/health/6180753.stm

(2) IQ scores are mostly inherited.

Evidence: http://en.wikipedia.org/wiki/Inheritance_of_intelligence
----------------------------------

(3) Vegetarians should be more likely to have vegetarian children than non-vegetarians.

What do you think?

Unit writes:

I get upset when they don't like the food I cooked! It's a question of pride. But if I didn't cook it, then they're allowed to push it back.

h-dawg writes:

"I have a ten year old daughter. I try to be as lenient and lax as possible, but the issue of food is an absolute nightmare."

I was generally lenient and lax with a very willful son who was causing increasing problems. His mom had the sense to suggest that his acting out was, in fact, a plea for stricter boundaries. It worked (he was quite a bit younger than 10 when he figured out I was no longer taking any sh*t from him). I still tended to look for reasons to 'yes' rather than 'no' to him, and he's still a bit on the wasteful and messy side, but his mom was basically right.

I have since noticed among my kid's friends--late teens, now--that the ones with the strictest upbringing are the nicest and best behaved. (Strict by NYC standards, anyway--we're not talking scowling Jesuits with bloody rulers, here.)

But I also thank my lucky stars that I had teenage sons instead of teenage daughters. Man.

ardyan writes:

Bryan,
In all your posts, you basic thinking goes "If your kid turns out badly, oh well, there was nothing you could do to change that". WRONG! You don't have to have the kid in the first place, which means the kids life doesn't turn out either bad or good, which I regard as the best outcome. Better to have missed out on mozart than to have given light to hitler.

Kurbla writes:

I agree with Greg: it is culture. Nurture cannot be reduced on parental influence.

Zac writes:

"Better to have missed out on mozart than to have given light to hitler."

This is, at best, some deeply flawed thinking, and at worst, profoundly anti-life and anti-human. On balance, people are good. In pursuit of their own narrow self interests, they benefit everyone through division of labor and trade. In the face of adversity, humanity has thrived, improved its lot, crushed those (like Hitler) who seek to reverse the progress we have made and revered those (like Mozart) who have contributed to our cultural history.

The good guys really are winning. We march forward. The more, the merrier.

Marc Resnick writes:

There are also influences more subtle, but perhaps more influential than nagging. Consider the studies that show the size of the plate we eat on and the amount of food eaten by others at the table (and in some studies at surrounding tables) has a significant impact on the amount of food we eat. These are short term studies, but they could add up if a family has a common practice. They could overwhelm any impact of nagging.

ardyan writes:

just to clarify, I am not saying that people are inherently evil, its just that I'm not the one who wants to wind up with a son or daughter who winds up having a miserable life or causing misery to others. I know the chance is small, but in my mind its big enough so that I feel its not worth the chance.

Jason Malloy writes:

Bryan, in all your parenting examples, the kids ore obedient and cooperative and the parents have these overly strict and out of date rules.

No, you are missing the point. The superfluous "overly strict" rules are only the ones intended to make the child's life turn out better, not the rules intended to make the parent's life better. That you can accomplish.

It sounds like your life would be easier if you introduced a slew of household rules; for example a kitchen closed policy, as mentioned by Scott in the first comment. Restore order to your home through reward and punishment; operant conditioning is your friend.

Tracy W writes:

Better to have missed out on mozart than to have given light to hitler.

Why?

Hitler killed a lot of people, yes. But Mozart will keep giving pleasure as long as humans have ears. Assuming of course, that people keep having children.

Perhaps you'd prefer a world full of merely rocks, rotating endlessly around the sun to a world full of suffering and pleasure, but I don't see why you think that any other view is just "WRONG!".

ardyan writes:

I didn't say any other view was wrong, I said that there was something you could do to to avoid having a kid turn up sour, which is to not have it in the first place. However, if having a kid is a must, then Bryan's view seems reasonable.

Wm Tanksley writes:

I recall a recent study -- quite well attested -- that showed that one's friends were the best predictor of one's weight.

So clearly it's not "genetic" (in any formal sense). Also, it's not family; it's who you choose to hang around, and THAT is something the family can to some extent influence.

Heh... "Don't go to Jimmy's house; we don't associate with His Type. He's Too Fat." :-)

-Wm

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