Snack cost and percentage of body fat in Chinese children and adolescents: a longitudinal study.

PURPOSE: Only a few studies examined the relationship between snack cost and change in the percentage of body fat in children. We thus conducted a longitudinal study to investigate whether high snack cost is associated with fast increase in the percentage of body fat in Chinese children. METHODS: The study included 2368 children (1126 girls and 1242 boys, aged 6-14 years). Percentage of body fat was repeatedly assessed by bioelectrical impedance analysis in 2014 (baseline), 2015 and 2016. Snack cost in 2014 was estimated by self-report associated with purchasing snacks at school and classified into low, moderate, and high group. Association between snack cost and repeated percentage of body fat was analyzed with linear mixed models, adjusting for demographic factors, diet, physical activity, and parental BMI and education. RESULTS: High snack cost was significantly associated with a fast increase in the percentage of body fat over time (p trend = 0.04). Adjusted difference in annual increase rate in percentage of body fat between the high and low snack cost group was 0.31% [95% confident interval (CI) 0.04%, 0.58%], after adjusting for potential confounders. The impacts of snack cost on change in the percentage of body fat were more pronounced in boys, younger participants and those with higher BMI z-score at the baseline, relative to their counterparts (p interaction < 0.001 for all). CONCLUSIONS: High snack cost was associated with more gain of body fat in Chinese school-aged children.