Snacking Is Longitudinally Associated with Declines in Body Mass Index Z Scores for Overweight Children, but Increases for Underweight Children

Background: Few studies, to our knowledge, have examined the longitudinal association of snacking with child body mass index (BMI), especially in China, where the incidence of overweight and obesity has increased rapidly.

Objectives: Our objective was to examine the longitudinal association between snacking and BMI z score and to test whether this association differs by baseline weight status.

Methods: Using data from the China Health and Nutrition Survey (2006, 2009, and 2011), we characterized snack intake for 9 provinces and 3 megacities. We used linear mixed-effects models to examine longitudinally the association between snacking (none, low, medium, and high tertiles according to energy) and BMI z score in children aged 2-13 y at baseline, controlling for sex, urbanicity, parental education, physical activity, and foods consumed at meals (n = 2277 observations). We tested whether this association differed by baseline underweight, normal weight, or overweight/obese.

Results: Snacking is prevalent in Chinese children, with fruit being the most common snack. Snacking was not associated with meaningful BMI z score changes in normal-weight children. However, in children who were underweight at baseline, snacking in the top tertiles was associated with increases in BMI z scores from 2006 to 2011 (+1.2 and +1.1 BMI z score units for ages 2-6 and 7-13 y, respectively) (P < 0.05). In overweight/obese 2- to 6-y-old children at baseline, being in the lowest snacking tertile was associated with declines in BMI z score (-3.3), whereas in overweight 7- to 13-y-old children, being in the top tertile of snacking was associated with the greatest decline in BMI z score (-2.1) (P < 0.05). The direction and magnitude of associations did not vary regardless of adjustment for total energy intake.

Conclusions: Snacking in China, dominated by fruit consumption, is associated with decreased BMI in overweight/obese children and increased BMI in underweight children. More work will be needed to monitor this relation as Chinese diets continue to westernize.