Association between household poverty dynamics and childhood overweight risk and health behaviours in the United States: a 8-year nationally representative longitudinal study of 16 800 children

Background: No study has examined how the pattern of income dynamics influences both of children's body mass index (BMI) trajectory and health behaviours. Objectives: To examine the association between household poverty dynamics and childhood overweight risk in the USA. Methods: Using the longitudinal data of 16 800 children (from kindergarten to the 8th grade) in the nationally representative US cohort-Early Childhood Longitudinal Study, Kindergarten Class 1998–1999, we examined the differences in BMI trajectory, weight-related health behaviours and risk of overweight in association with household poverty dynamics during follow-up (never [no experience of poverty], transient [once], recurrent [≥2 times] and persistent poor [remained]) using mixed models with fractional polynomial functions and estimating equation models. Results: Overall, children experiencing poverty were more likely to have adverse BMI growth trajectory and eating and sedentary behaviours compared with the never poor. The recurrently poor children (12.8%) had the fastest BMI trajectory, highest overweight/obesity prevalence from 5 to 16 years old and highest proportion of excessive soda/fast food consumption and irregular exercise at 8th grade than did others (p < 0.05). The persistently poor (8.4%) were the lowest in BMI growth trajectory but became the second highest in childhood obesity through a steady increase in BMI over time. Children in the recurrently poor group had a 1.5 times (95% CI = 1.0–2.2) higher risk of overweight than those having never experienced poverty during follow-up. Conclusions: The experience of recurrent household poverty had a significant association with children's adverse eating behaviours and increased obesity risk subsequently.