en <span style=font-size:11pt><span style=line-height:normal><span style=unicode-bidi:embed><span style=font-family:Calibri,sans-serif><b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:#4472c4>Aims:</span></span></span></b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:black> This study aimed to assess the effectiveness of an intervention on fiber consumption, self-efficacy, perceived benefit, and barriers among the elderly using the Trans-theoretical Model (TTM). </span></span></span></span></span></span></span><br> <span style=font-size:11pt><span style=line-height:normal><span style=unicode-bidi:embed><span style=font-family:Calibri,sans-serif><b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:#4472c4>Materials & Methods:</span></span></span></b><b> </b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:black>This quasi-experimental study was developed among constipated elderly people aged ≥60 in Karaj, Iran, between 2019 and 2021. Constipated participants were randomly assigned to the intervention (n=66) or the control (n=64) groups. Before and after four educational sessions, demographic information, participants’ stages of change for diet, self-efficacy, decisional balance, and daily amount of fiber consumption were evaluated. An analysis was performed to assess any differences in the stages of change (posttest vs. baseline).</span></span></span></span></span></span></span><br> <span style=font-size:11pt><span style=line-height:normal><span style=unicode-bidi:embed><span style=font-family:Calibri,sans-serif><b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:#4472c4>Findings: </span></span></span></b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:black>The perceived barriers and self-efficacy were statistically significant after intervention (p<0.001) in the intervention group compared to the control group (p>0.001). In both groups, perceived benefits changed statistically significantly (p<0.001). Pearson correlation also showed a significant correlation between stages of change and benefits, barriers, self-efficacy, and fiber consumption. The analysis of variance adjusting for covariates also indicated significant differences between intervention and control groups.</span></span></span><b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:#4472c4></span></span></span></b></span></span></span></span><br> <span style=font-size:11pt><span style=line-height:normal><span style=unicode-bidi:embed><span style=font-family:Calibri,sans-serif><b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:#4472c4>Conclusion: </span></span></span></b><span style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:black>The TTM is a useful model that can be applied to dietary behavior change, specifically fruit and vegetable consumption among elderly populations.</span></span></span><span lang=EN style=font-size:10.0pt><span style=font-family:Cambria,serif><span style=color:black></span></span></span></span></span></span></span><br> Aged,Constipation,Dietary Fiber,Health Education,Transtheoretical Model, 485 492 http://hehp.modares.ac.ir/browse.php?a_code=A-10-67612-3&slc_lang=en&sid=4 M. Ghanbari 1003194753284600300498 1003194753284600300498 No Department of Health Education and Health Promotion, School of Health, Alborz University of Medical Sciences, Karaj, Iran F. Rajati 1003194753284600300499 1003194753284600300499 No Research Center for Environmental Determinants of Health, Kermanshah University of Medical Sciences, Kermanshah, Iran L. Salehi 1003194753284600300500 1003194753284600300500 Yes Research Center for Health, Safety and Environment, Health Education and Promotion, Alborz University of Medical Sciences, Karaj, Iran