Kids are terrible at understanding their own weight

From last month’s Academic Pediatrics, “Accuracy of Weight Perceptions in a Nationally Representative Cohort of US 8th Grade Adolescents“:

Objective: To describe the accuracy of weight perceptions in a nationally representative sample of US 8th graders, its relationship with weight control intentions (WCI), and the relationship of weight misperceptions and WCI with diet and activity behaviors.

Methods: Data analyzed came from the 8th grade wave (2006–2007) of the Early Childhood Longitudinal Study–Kindergarten Class, a nationally representative sample. Body mass index was calculated from height and weight measurements for 7800 8th graders (mean age 14.3 years). Measured weight status was categorized into underweight, normal weight, overweight, and obese using the US Centers for Disease Control and Prevention’s age- and sex-specific growth charts. Self-reported weight status was compared with measured weight status to classify adolescents into accurate perceivers, overestimators, and underestimators. Multivariate logistic and negative binomial regression models were estimated for binary and count data outcome variables, respectively.

It’s no secret that overweight and obesity are a major problem in kids. About 1 in three children are currently in one of those classes in the US. Being overweight or obese as a child makes one more likely to be obese as an adult, which of course carried with it its own health risks.

Many people think it’s all about giving people knowledge about what they’re eating so that they can make better choices in the future. But, of course, that’s predicated on the belief that those who are at risk KNOW that they’re at risk, so that they can use the knowledge you’re giving them.

Researchers in this study used data from the Early Childhood Longitudinal Study-Kindergarten Class. It started back in 1998-1999, and data have been collected at baseline, and then in grades 1,3,5, and 8. This study focused on the eighth grade wave. Besides collecting data from the kids, parents, and teachers, height and weight were also collected.

Data from about 7800 kids average age just over 14 years were available. That was about 43% of the kids from the original kindergarten class. Most of those kids who were lost to follow-up had changed schools. They were more likely to be black and of lower socioeconomic status relative to those in this study, but there were no statistically significant differences in BMI, obesity prevalence, sex, or age in kindergarten of those still in and out of the cohort.

The data were weighted so that they represented, and I’m quoting the paper, “3,417,969 adolescents in the United States, or about 80% of all US 8th graders in the 2006-2007 school year.” I love the precision there.

Overall, about 42% of the adolescents didn’t perceive their weight status accurately. Just over 35% underestimated it, and just under 7% overestimated it. The real concerning part, though, is that most of the misperception is among those who are overweight or obese.

More than half of overweight adolescents underestimated their weight status. Just under half thought they were normal weight, and more than 3% thought they were underweight. More than 78% of obese adolescents, though, underestimated their weight status. About 60% of them thought they were just overweight, and another 16% thought they were normal weight. 2% more thought they were underweight.

Unhealthy behaviors were associated with underestimating weight. Adolescents who did underestimate their weight ate 38% more fast food and bought 37% more junk food at school.

Interestingly, adolescents who reported trying to lose weight were not significantly different from those who were not with respect to their diet and activity behaviors. I’m not even sure what to do with that. Thinking about the fact that those who were “trying to lose weight” weren’t acting or eating any differently from those who weren’t makes my head hurt.

It’s all well and good to keep putting data and calorie counts in front of people, including adolescents. But it doesn’t seem to be helping. It’s going to be even harder when so many of them don’t see the problem existing in the first place.


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