Study: Obesity epidemic partly explained by erroneous data

A new study in the American Journal of Epidemiology indicates that parent-reported height/weight data for children isn’t all that reliable. We have always been critical of self-reported obesity data.

The abstract is below.

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Parent-Reported Height and Weight as Sources of Bias in Survey Estimates of Childhood Obesity

Margaret M. Weden*, Peter B. Brownell, Michael S. Rendall, Christopher Lau, Meenakshi Fernandes and Zafar Nazarov

↵*Correspondence to Dr. Margaret M. Weden, Rand Corporation, 1776 Main Street, Santa Monica, CA 90401-3208 (e-mail: mweden@rand.org).

Abbreviations: BMI, body mass index; CDC, Centers for Disease Control and Prevention; CI, confidence interval; NLSY79, National Longitudinal Survey of Youth 1979 Cohort; NLSY79-Child, Children of the National Longitudinal Survey of Youth 1979 Cohort; PSID-CDS, Child Development Supplement of the Panel Study of Income Dynamics.

Received June 26, 2012.
Accepted December 3, 2012.
Abstract

Parental reporting of height and weight was evaluated for US children aged 2–13 years. The prevalence of obesity (defined as a body mass index value (calculated as weight (kg)/height (m)2) in the 95th percentile or higher) and its height and weight components were compared in child supplements of 2 nationally representative surveys: the 1996–2008 Children of the National Longitudinal Survey of Youth 1979 Cohort (NLSY79-Child) and the 1997 Child Development Supplement of the Panel Study of Income Dynamics (PSID-CDS). Sociodemographic differences in parent reporting error were analyzed. Error was largest for children aged 2–5 years. Underreporting of height, not overreporting of weight, generated a strong upward bias in obesity prevalence at those ages. Frequencies of parent-reported heights below the Centers for Disease Control and Prevention’s (Atlanta, Georgia) first percentile were implausibly high at 16.5% (95% confidence interval (CI): 14.3, 19.0) in the NLSY79-Child and 20.6% (95% CI: 16.0, 26.3) in the PSID-CDS. They were highest among low-income children at 33.2% (95% CI: 22.4, 46.1) in the PSID-CDS and 26.2% (95% CI: 20.2, 33.2) in the NLSY79-Child. Bias in the reporting of obesity decreased with children’s age and reversed direction at ages 12–13 years. Underreporting of weight increased with age, and underreporting of height decreased with age. We recommend caution to researchers who use parent-reported heights, especially for very young children, and offer practical solutions for survey data collection and research on child obesity.

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5 responses to “Study: Obesity epidemic partly explained by erroneous data

  1. Maybe the real problem is illiteracy.

  2. Half of the people have below average intelligence and can only read at the 6th grade level. No answers to researcher questions can be trusted.

  3. “The prevalence of obesity (defined as a body mass index value (calculated as weight (kg)/height (m)2) in the 95th percentile or higher)…” That would seem to define the 95+ percentiles as obese regardless of the actual BMI or medical indicators. That’s sort of like saying the bottom 10% of income earners must be poor without evaluating the purchasing power of the lowest decile.
    There might be value in defining the BMI that ranks as the 95th percentile and tracking changes in that BMI from reliable data. But this discussion ain’t it.

  4. luisadownunder

    I always wanted my children to be taller and weigh less ;)

  5. I am amazed that people believe in the childhood obesity epidemic, when the evidence of their own eyes must reveal it to be a fraud. I’m pretty sure that researchers who insist that 30 percent of children are overweight or obese have chosen that figure before collecting any data at all. They have just settled on a figure that is alarming but also plausible enough that people will believe it. Anyone who goes to an elementary school yard and looks at the children on its playground during recess can easily see that is just not true that 30 percent of children are what any reasonable person would call fat.

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