Effect of Motivational Interviewing on a Weight Loss Program Based on the Protection Motivation Theory

The prevalence of overweight and obesity is on the increase the world over, which imposes an ever-increasing burden on societies and health care systems. This study sought to investigate the effect of motivational interviewing (MI) on a weight-loss program based on the protection motivation theory (PMT). This randomized clinical trial study, comprising pretest-posttest with a control group, was conducted on 150 overweight and obese women attending a private nutrition clinic for the first time. Samples were randomly selected using the clinic’s records and then allocated to three groups (50 women in each group) receiving: 1) a standard weight-control program; 2) motivational interviewing; and 3) MI plus intention intervention. Data were collected using a researcher-made questionnaire through in-person interviews and were analyzed using SPSS (version 11) and statistical tests, including the Kruskal-Wallis test, one-way analysis of variance, paired t-test, and linear regression model. In the two intervention groups, the PMT construct scores, namely susceptibility (P = 0.001), severity (P = 0.001), rewards (P =0.004), self-efficacy (P = 0.001), response efficacy (P = 0.001), and costs (P = 0.014), were significantly increased compared to those in the control group. The anthropometric status was statistically significant in the MI group (P = 0.001) and the MI plus intention-intervention group (P = 0.001) at 2 months’ follow-up, while in the control group, weight was meaningfully different after the intervention (P = 0.027). Weight was different between the groups after the intervention, with the Tukey test demonstrating that the differences were statistically significant between the control group and the MI group. Our results demonstrated that MI, combined with the implementation of intention intervention, increased weight loss and PMT construct scores in our study population