The XX Factor

Your Fat Baby Is Probably Fine

Just how predictive are early weight-to-height ratios for infants?

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Researchers at Harvard University published a study this week showing that babies whose weight-to-height ratio jumps two percentile groups before the age of 2 are more likely to be obese later in childhood, according to an AP article making the rounds.

The results of the study are both strikingly obvious—if your baby gains weight more quickly than other babies, he is more likely to be fat later on—and fairly inconclusive. The supposed upshot of the doctors’ research, conducted by parsing the growth charts of 45,000 Boston-area children over the course of 18 years, is that infants who gain weight rapidly are at a higher risk of childhood obesity. However, only 12 percent of the infants in the authors’ designated high-risk group were obese by the age of 5, which—considering that 10 percent of all preschool-aged children are obese—means that the authors’ suggested predictive tool isn’t really all that predictive.

So why has the national press enthusiastically picked up on a study that’s neither surprising nor particularly convincing? Could it just maybe be that obesity is such a reliably hot-button topic that newspapers and magazines will publish virtually any ostensibly scientific information on it?

The new study, which was published in the Archives of Pediatrics and Adolescent Medicine (alongside an editorial criticizing its suggestions), is a link-bait double whammy, since its conclusions stoke parenting fears just as much as body-image anxieties. And the AP article lays out the impossible tightrope parents feel pressured to walk when it comes to their children’s health: If your baby’s gaining weight too quickly, she’ll probably be obese later on, but if you put her on a diet, you’ll set her up for a lifetime of unhealthy eating patterns.

This paradox arises from the assumption—which goes unchallenged in virtually all mainstream reporting of obesity—that only thin (but not too thin!) people can be healthy. In reality, healthy bodies come in all shapes and sizes, as do unhealthy bodies, and no single ideal size applies to everyone (even to all babies). But researchers would get a lot less funding, science journalists would get a lot fewer assignments, and the diet industry would make a lot less profit if people started believing that.