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Background and Objective: Obesity presented as the most pivotal public health problem. Motivational interviewing is a client-centered and direct technique to improve intrinsic motivation of people to change behavior using search and resolve ambivalence that its beneficial outcomes have widely been confirmed. This study was carried out to evaluate the effect of motivational interviewing on weight loss in women. Methods: In this randomized clinical trial study, 150 women with overweight and obesity were randomly divided into control, motivational interviewing and motivational interviewing and intention implementation groups. Data were collected through a researcher made questionnaire at baseline and 2 month follow up. Results: The score of protection motivation theory constructs including susceptibility, severity, rewards, self-efficacy, response efficacy and cost were significantly increased in the two intervention groups compared to the control group (P<0.05). Anthropometric characteristics were significantly reduced in the motivational interviewing and motivational interviewing with intention implementation group (P<0.05) in compare to the control group (P<0.05). Conclusion: Motivational interviewing integrated into intention implementation causes weight loss and increase the constructs score in women.