Longitudinal associations between overweight/obesity and stress biology in low-income children

Associations between overweight and altered stress biology have been reported cross-sectionally during childhood, but it is unclear whether overweight precedes altered stress biology or if altered stress biology predicts greater likelihood of overweight over time. The current longitudinal study investigates associations between overweight/obesity, salivary alpha amylase and cortisol morning intercept, diurnal slope, and reactivity to social stress in a cohort of low-income children during preschool and middle childhood. Children were recruited through Head Start and were observed and followed into middle childhood (N = 257; M = 8.0 years). Height and weight were measured at both time points. Saliva samples were collected across the day and in response to a social challenge at both ages for alpha amylase and cortisol determination. Cross-lagged panel analyses indicated that overweight/obesity at preschool predicted lower morning alpha amylase (β = −0.18, 95% CI: −0.34, −0.03; p = 0.023), lower morning cortisol (β = −0.22, 95% CI: −0.38, −0.06; p = 0.006), lower sAA diurnal slope (β = −0.18, 95% CI: −0.34, −0.03; p = 0.021), and lower cortisol stress reactivity (β = −0.19, 95% CI: −0.35, −0.02; p = 0.031) in middle childhood. Lower alpha amylase reactivity at preschool was the only biological factor that predicted higher likelihood of overweight/obesity at middle childhood (β = −0.20, 95% CI: −0.38, −0.01; p = 0.035). These findings suggest that overweight/obesity may be driving changes in stress biology across early-to-middle childhood, particularly in downregulation of morning levels of stress hormones, diurnal sAA slope, and cortisol reactivity to stress, rather than stress biology driving overweight/obesity.