Background There is a dearth of evidence on whether better psychological well-being is associated with likelihood of returning to healthy weight after developing overweight or obesity in children. This study aimed to examine the associations between psychological well-being related measures and ‘reversal’ (returning to healthy weight) vs. persistence of overweight or obesity.

Methods This longitudinal study included UK children with overweight or obesity from the Millennium Cohort Study. Weight changes from baseline at ages 11 (n = 4,556; 6-year follow-up) and 14 (n = 3,791; 3-year follow-up) to follow-up at age 17 were presented as 1) reversal (vs. persistence) of overweight or obesity and 2) residualised change body mass index (BMI) z-scores. To account for ‘overall’ psychological well-being, two distinct indexes were developed by combining baseline individual psychological well-being related measures, guided by exploratory factor analysis. These indexes were 1) caregiver-reported child mental health (internalising and externalising symptoms) and 2) child-reported psychosocial well-being (self-esteem, depressive symptoms, life satisfaction, appearance satisfaction, and peer bullying). Higher index scores indicated better child mental health and psychosocial well-being. Regression models examined the associations between baseline psychological well-being related measures (indexes and individual measures) and weight changes, controlling for sociodemographic characteristics and pubertal status.

Results Better caregiver-reported child mental health and child-reported psychosocial well-being at age 11 were independently associated with increased likelihood of reversal vs. persistence (OR = 1.16; 95%CI = 1.03, 1.29; and OR = 1.29; 95%CI = 1.15, 1.44; respectively) and decreased BMI z-scores (β = -0.08, 95%CI= -0.13, -0.03; and β = -0.07, 95%CI = -0.11, -0.03; respectively) to age 17. However, neither was associated with weight changes when measured at age 14. Findings were consistent when individual psychological well-being related measures were examined (as opposed to indexes). Additional/sensitivity analyses between psychological well-being related measures and timing of measures indicated that psychological well-being related measures were more likely to be associated with weight changes when measured at age 11 compared to age 14, suggesting late childhood or early adolescence (age 11) may be a sensitive period in which psychological well-being have a more pronounced prospective association with body weight outcomes.

Conclusion Better psychological well-being at age 11 is associated with increased likelihood of reversing childhood overweight or obesity by age 17. Findings inform the potential importance of integrating psychological support into current obesity prevention or weight loss strategies (improving diet and physical activity) for children, particularly during an age-specific sensitive period (age 11).