Moderators of two dual eating disorder and obesity prevention programs

Abstract

Few trials have investigated factors that moderate the effects of eating disorder and obesity prevention programs, which may inform inclusion criteria and intervention refinements. We examined factors hypothesized to moderate the effects of the Healthy Weight eating disorder/obesity prevention program that promotes gradual healthy changes, and Project Health that adds cognitive dissonance activities. College students at risk for both outcomes because of weight concerns (N = 364, 72% female) were randomized to these interventions or an educational video condition, completing pretest, posttest, and 6, 12, and 24-month follow-up assessments. Healthy Weight and Project Health produced significantly larger reductions in eating disorder symptoms versus video controls for individuals with higher negative affect, emotional eating, dietary fat/sugar intake, and perceived pressure to be thin. Project Health also produced significantly less increases in BMI versus video controls for individuals with lower negative affect. Results suggest that these interventions produce larger eating disorder symptom reductions for individuals at elevated risk for eating pathology but hint that weight gain prevention effects may be attenuated by elevated negative affect. Results imply that larger eating disorder symptom reductions will result when implemented with individuals with both weight concerns and one of the additionally identified risk factors.

Trial registration: ClinicalTrials.gov NCT01680224.

Keywords: Dissonance; Eating disorders; Moderators; Obesity; Prevention.

Copyright © 2019. Published by Elsevier Ltd.

Figures

Figure 1.

Mean growth curve for BMI and eating symptoms by conditions. Note. Pre refers to start of the intervention; Post to the end of the intervention; and 6 month, 12 month, and 24 month to the follow ups.

Figure 2.

Region of significance plot for the difference in the simple slope of BMI between Project Health and educational video participants as a function of negative affect. Note. When the solid line is above zero, Project Health participants had a greater BMI slope than video participants, whereas when the line is below zero, educational video participants had a significantly greater BMI slope than Project Health participants. Where the dashed lines do not overlap with zero (the white region), this indicates a significant difference between the conditions at that level of the moderator. The percent of the sample and numbers of participants in each of the three columns are presented along the top of the figure.

Figure 3.

Region of significance plots for the difference between Project Health and educational video participants for the two significant moderators. Note. When the solid line is above zero, video participants had a greater reduction in eating symptoms than Project Health participants, whereas when the line is below zero, Project Health participants had a greater reduction in eating symptoms than video participants. Where the dashed lines do not overlap with zero (the white regions), this indicates a significant difference between the conditions at that level of the moderator. The percent of the sample and numbers of participants in each of the three columns are presented along the bottom of the figures.

Figure 4.

Region of significance plots for the difference between Healthy Weight and educational video participants for the four significant moderators. Note. When the solid line is above zero, video participants had a greater reduction in eating symptoms than Healthy Weight participants, whereas when the line is below zero, Healthy Weight participants had a greater reduction in eating symptoms than video participants. Where the dashed lines do not overlap with zero (the white regions), this indicates a significant difference between the conditions at that level of the moderator. The percent of the sample and numbers of participants in each of the three columns are presented along the bottom of the figures.

Figure 5.

Region of significance plots for the difference between Project Health and educational video (top) and Healthy Weight educational video (bottom) participants for the composite moderator. Note. When the solid line is above zero, video participants had a greater reduction in eating symptoms than Project Health participants, whereas when the line is below zero, Project Health participants had a greater reduction in eating symptoms than video participants. Where the dashed lines do not overlap with zero (the white regions), this indicates a significant difference between the conditions at that level of the moderator