Purpose: This study aims at identifying behavioural and psychological pretreatment predictors of 12- and 36-month weight loss in women with overweight/obesity enrolled in a behavioural weight management intervention.
Methods: A sample of 221 women participated in a randomized controlled trial on weight management (n12 month = 184; n36 month = 156). Multiple linear regressions were used to identify pretreatment predictors of successful weight loss, separately for intervention and control groups. Completers-only and baseline observation carried forward analyses were performed. This study is a secondary analysis of data from the 'Promotion of Exercise and Health in Obesity' randomized controlled trial.
Results: Fewer weight loss attempts in the last year positively predicted weight loss at 12 months in the intervention group, explaining 6% of the variance. At 36 months, in the intervention group, 20.2% of the variance in weight change was explained by lower eating disinhibition and higher weight-related quality of life in completers-only analyses, while baseline observation carried forward analyses explained only 9.8% of the variance in weight change via higher self-esteem and lower weight loss expectations. In the control group, higher exercise self-efficacy and a more internal weight locus of control predicted weight loss at 36 months, explaining 13.9% of the variance (completers-only analyses).
Conclusions: Previous weight loss attempts were identified as the most efficient pretreatment predictor of 12-month weight loss. Eating disinhibition, weight-related quality of life, self-esteem, weight loss expectations, exercise self-efficacy, and weight locus of control seem to be key factors for long-term success.
Level of evidence: Level I, randomized controlled trial.
Clinical trial registration: ClinicalTrials.gov identifier NCT00513084.
Keywords: Clinical trials; Obesity; Overweight; Prediction; Weight loss; Women.