The Effects of If-Then Plans on Weight Loss: Results of the McGill CHIP Healthy Weight Program Randomized Controlled Trial

Abstract

Objective: The NIH-developed Diabetes Prevention Program (DPP) is successful in achieving clinically significant weight loss in individuals with overweight/obesity when delivered one-on-one. The group-based DPP is less effective, with average weight losses of only 3.5%. The objective of this study was to increase weight loss outcomes of the group-based DPP by integrating habit formation tools (i.e., if-then plans). This two-arm randomized controlled trial tested the efficacy of the habit formation–enhanced group-based DPP compared with the standard group-based DPP on changes in body weight (primary outcome). This study presents the 3- and 12-month results of this 24-month trial. Methods: A total of 208 participants were randomly assigned to the standard or enhanced DPP, and 172 participated. Participants were men and women with overweight/obesity who self-reported less than 200 min/wk of exercise. Results: Both groups achieved high weight losses at 3 (5.76%) and 12 (9.98%) months, with no differences between groups (χ2 < 1). Both groups improved in blood pressure and physical activity. Conclusions: If-then plans did not result in higher weight loss. Both program versions resulted in higher weight loss than the group-based DPP. This may suggest that cognitive behavioral therapy skills of the coaches (clinical psychology doctoral students) was a key factor in treatment outcome.