A Theory of Planned Behavior-Based Program to Increase Physical Activity in Overweight/Obese Military Personnel: A Randomised Controlled Trial Hormoz Sanaeinasab, Mohsen Saffari* , Mohammad-ali Dashtaki and Aliakbar Karimi Zarchi Baqiyatallah University of Medical Sciences, Iran Amir H. Pakpour Qazvin University of Medical Sciences, Iran J€ onk€ oping University, Sweden Keisha-Gaye N. O'Garo Duke University Medical Center, USA Harold G. Koenig Duke University Medical Center, USA King Abdulaziz University, Saudi Arabia Ningxia Medical University, China Background: Designing a health promotion program to increase physical activity may contribute to weight management. The purpose of this study was to investi- gate a theory of planned behavior (TPB) program to address this problem in mili- tary people. Methods: Eighty-four obese/overweight military personnel were randomised into the intervention or control group. A questionnaire assessed demo- graphics, aspects of the TPB program, and physical activity levels. Also assessed were blood glucose and lipid levels. The intervention consisted of seven educa- tional sessions based on TPB. Data were collected at baseline and 3 months after the intervention. Results: All constructs of the TPB improved between baseline and follow-up in the intervention group (p < .001), while there were no significant changes in the control group (within-group comparisons). Between-group *Address for correspondence: Mohsen Saffari, Health Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran; and, Health Education Department, Faculty of Health, Baqiyatallah University of Medical Sciences, Tehran, Iran. Emails: m.saffari@ bmsu.ac.ir and Saffari.CHES@gmail.com APPLIED PSYCHOLOGY: HEALTH AND WELL-BEING, 2019 doi:10.1111/aphw.12175 © 2019 The International Association of Applied Psychology