Online Mental Contrasting with Implementation Intentions for changing snacking behavior and reducing body mass index in people with excess weight: a randomized controlled trial

Abstract

Mental Contrasting with Implementation Intentions (MCII) has proved useful for dietary changes, but not yet applied to people with excess weight. We aimed to determine the benefit of online MCII as an add-on to a standard Behavioral Weight Loss Intervention (Treatment as Usual-TAU) to change snacking behavior -one of the main contributors to excess weight- and reduce BMI. This online randomized controlled trial included 148 participants [MCII-group (50), Sham-group (50) and TAU-group (48)]. All participants received standard intervention: motivational interviewing, individualized diet and physical exercise. MCII and Sham groups received training for one week, while TAU-group had monitoring. Outcome measures were self-reported snacking behavior (frequency of snacking, total servings, ultra-processed food -UPF- servings) and BMI. Results of mixed ANOVAS showed interactions group x time (pre-vs post-treatment) for all variables: frequency of snacking [F (2,134) =6.110, p =.003], total servings [F (2,126) =4.291, p =.016], UPF servings [F (2,127) = 4.059, p =.020], and BMI [F (2,98) =3.990, p =.022]. The MCII-group showed differences with Sham and TAU groups at post-treatment in all snacking behavior variables, with large effect sizes between the MCII-group and the other two groups, and null between Sham and TAU groups (except for UPF servings). Complimentary one-way ANOVA for standardized change showed greater BMI reductions for the MCII-group [F (2,103) =3.990, p =.006], with moderate effect sizes. In conclusion, MCII improves the results of usual treatment for excess weight in snacking behavior and BMI. Trial registration: Clinical Trials NCT05158075.