Elevated parent and child hair cortisol moderated the efficacy of a mindful eating intervention.

To explore whether elevated baseline hair cortisol moderated effects of a mindful eating intervention on anthropometrics, blood pressure (BP), household food insecurity, eating behaviour, and various psychosocial outcomes. The 14-week intervention included a parent Facebook-based programme, 3 parent meetings, preschooler letters connecting school learning to home practices, and a preschool-based mindful eating programme. Among 107 parent-preschooler dyads, mean age was 47.32 months for preschoolers and 30.12 years for parents. Among preschoolers, 54.2% were female, 8.4% were Hispanic, and 19.6% were Black. Among parents, 95.3% were female, 6.5% were Hispanic, 15.0% were Black, 39.4% were single, and 43.4% were unemployed. Preschoolers' elevated hair cortisol was related to a smaller reduction in preschoolers' % body fat (r =.31) and smaller increases in parents' perceived responsibility for child feeding (r = -.37). Parents' elevated hair cortisol was associated with smaller decreases in preschoolers' emotional eating (r = .39) and household food insecurity (r = .44). Relationships between baseline hair cortisol and post-intervention outcomes (BP, emotional eating, fruit/vegetable intake, food insecurity, and coping) varied by baseline values of outcome variables. Given that stress may attenuate intervention effects, a stress management component may be necessary to foster positive behavioural changes. Moreover, interventions should be tailored according to participants' characteristics to achieve optimal effects.