Conflicting evidence exists as to whether cognitive mechanisms contribute to weight loss and maintenance.

To assess the influence of weight-loss expectations on weight loss, and of weight-loss satisfaction on weight maintenance, in individuals with severe obesity.

A randomized controlled trial comparing two types of energy-restricted diets (high protein vs high carbohydrate) combined with weight-loss cognitive behavioral therapy, conducted over 51 weeks and divided into two phases: weight-loss phase (3 weeks of inpatient treatment and 24 weeks of outpatient treatment) and weight maintenance phase (24 weeks of outpatient treatment).

Eighty-eight participants with severe obesity (mean age=46.7 years and mean body mass index=45.6), referred to an eating and weight disorders clinical service, were studied.

Body weight was assessed at baseline, and after 3, 27 (end of weight-loss phase), and 51 weeks (end of weight maintenance phase). Weight loss expectations were assessed at the time of enrollment, and weight-loss satisfaction was assessed after 27 weeks.

The relationship between weight-loss expectations and weight loss was assessed using a linear mixed model. The association between weight-loss satisfaction and final outcomes was tested by linear regression.

The two groups had similar weight-loss expectations and satisfaction, and their results were therefore pooled. In general, the total amount of expected weight loss (in kilograms), but not the percentage of expected weight loss, predicted weight loss, and both satisfaction with weight loss and the amount of weight lost (in kilograms) were independent predictors of weight maintenance.

Higher expected weight loss improves weight loss, and both the total amount of weight lost and satisfaction with weight loss are associated with weight-loss maintenance at 1-year follow-up.