en تخصصي Special پژوهشي Research <strong>Objective:</strong> Overweight and obesity described as the most serious public health issues that can lead to long-term consequences .This study conducted to investigate whether breastfeeding has a preventing effect on the prevalence of overweight and obesity in adulthood.<br> <strong>Materials and Methods:</strong> This descriptive cross-sectional study was performed on students in Shahid Sadoughi University of Medical Sciences (n=300) in 2013. Data were collected through cluster sampling method. Data was collected via a researcher made checklist. Data was analyzed using descriptive statistics, t-test, chi square and ANOVA in SPSS-16 software.<br> <strong>Results:</strong> The mean (&plusmn;Standard Deviation) of body mass index (BMI) of students were 21.91 &plusmn; 0.4 kg/m². The mean BMI of men was significantly higher than women<strong>. </strong>The prevalence of overweight and obesity was 16.7%. Based on the result, approximately 96.4% of the children had been ever breastfed; 11.1% of the children were breastfed for less than 6 months. Researcher found no association between the duration or exclusivity of breastfeeding and obesity and overweight in later life.<br> <strong>Conclusion</strong><strong>:</strong> The results of our study did not show a significant association between the duration or exclusivity of breastfeeding and BMI in young adulthood<strong>.</strong> Bottle feeding, Breast feeding, Obesity, Overweight 1 5 http://ijdo.ssu.ac.ir/browse.php?a_code=A-10-30-161&slc_lang=en&sid=1 Mahdieh Momayyezi Yes M.Sc of Health Education, Prevention and Epidemiology of Non -Communicable Disease Research center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Hossein Fallahzadeh No Professor, Prevention and Epidemiology of Non-Communicable Disease Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Hamideh Nasirzadeh No Faculty of Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran