Child BMI over time and parent-perceived overweight

BACKGROUND AND OBJECTIVES: Parents often do not accurately perceive overweight and/or obesity in their children. Changing this is widely considered an essential first step to reducing child overweight, but recent research suggests that, in fact, this could promote greater weight gain. We aimed to determine the directionality over time between higher child adiposity and parental perception of child overweight.
METHODS: Participants were from 2 cohorts of the population-based Longitudinal Study of Australian Children followed biennially since 2004. Repeated measures of BMI z scores and parental perceptions of overweight were available for the kindergarten cohort at 6 waves (ages 4-5, 6-7, 8-9, 10-11, 12-13, and 14-15 years; n = 4632) and for the birth cohort at 4 waves (ages 2-3, 4-5, 8-9, and 10-11 years; n = 4445). Bidirectionality between overweight perception and BMI z score was examined by using cross-lagged regression models.
RESULTS: In both cohorts, wave-on-wave lagged effects were strong (all: P <.001) but much larger from BMI z score to parent perception. For every unit increase in the BMI z score, the odds of a child being perceived as overweight in the next wave ranged from 2.9 (birth cohort: Age 2-3 years) to 10.4 (kindergarten cohort: Age 6-7 years). These effects were ∼3 to 12 times larger than the reverse, whereby the perception of overweight predicted 0.2 to 0.5 higher BMI z score in the next wave.
CONCLUSIONS: Higher child BMI z scores strikingly predicted a subsequent parental perception of child overweight. Parent-perceived overweight preceded rising (not falling) BMI, but these effects were small. Clinician efforts to make parents aware of overweight may not be harmful but seem unlikely to improve children's BMI status.