OBJECTIVE: Despite the promising results related to intuitive eating, few studies have attempted to explain the processes encouraging this adaptive eating behaviour. The focus of the present study was on exploring mechanisms of change in intuitive eating and weight in acceptance and commitment therapy (ACT) interventions. Mediation provides important information regarding the treatment processes and theoretical models related to specific treatment approaches. The study investigates whether psychological flexibility, mindfulness skills and sense of coherence mediated the interventions' effect on intuitive eating and weight.

DESIGN: Secondary analysis of a randomized control trial. Mediation analysis compared two ACT interventions - face-to-face (in a group) and mobile (individually) - with a control group using a latent difference score model. Settings Data were collected in three Finnish towns.

SUBJECTS: The participants were overweight or obese (n 219), reporting symptoms of perceived stress.

RESULTS: The effect of the interventions on participants' (i) BMI, (ii) intuitive eating and its subscales, (iii) eating for physical rather than emotional reasons and (iv) reliance on internal hunger and satiety cues was mediated by changes in weight-related psychological flexibility in both ACT groups.

CONCLUSIONS: These findings suggest that ACT interventions aiming for lifestyle changes mediate the intervention effects through the enhanced ability to continue with valued activities even when confronted with negative emotions and thoughts related to weight.