en Endocrinology Endocrinology Original Research Original Research <p> <strong> Background: </strong>Increase in prevalence of obesity and type 2 diabetes which are of the main risk factors of metabolic syndrome, is not only the result of changes in genetic, diet or physical activity, but also an imbalance of micro flora may play an important role. Therefore, alteration of micro flora using pre/probiotic is considered as a new strategy for treatment of metabolic disorders. </p><p> <strong> Methods </strong>: The current study is a triple blind randomized controlled trial. 46 patients from both sexes, who fulfilled inclusion criteria, randomly categorized into intervention or placebo group. The intervention and placebo groups consumed 2 probiotic capsules or 2 placebo capsules during 3 months, respectively. Both groups received a weight loss diet, according to their adjusted ideal body weight. Anthropometric, body composition, blood pressure and nutritional measurements were done in the beginning, at 6th week, and at the end of the study. T-test and paired-t test were used for statistical analysis. </p><p> <strong> Results </strong>: 40 patients completed the study. BMI, WC, HC, fat mass, lean mass and blood pressure were reduced in all participants (p<0.05). Systolic blood pressure in symbiotic group was less than placebo group, significantly (p<0.05). The trend of weight loss in symbiotic group continued at least for 12 weeks while it was stopped at week 6 in placebo group. </p><p> <strong> Conclusion </strong>: Symbiotic supplement with the weight loss diet had synergistic effects on improvement in systolic blood pressure and anthropometric measurements. Based on our findings, symbiotic can postpone plateau phase of weight loss and it may prevent resistance to further weight loss. </p><p>  </p> Metabolic syndrome, Gut micro flora, Symbiotic, Body composition. 433 440 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-837&slc_lang=en&sid=1 Samira Rabiei samirarabiei@yahoo.com 200319475328460016586 200319475328460016586 No Department of Clinical Nutrition & Dietetics, ShahidBeheshti University of Medical Sciences, Tehran, Iran. Rahebeh Shaker Hosseini rshakerhosseini@yahoo.com 200319475328460016587 200319475328460016587 Yes Shahid Beheshti University of Medical Sciences, Tehran, Iran. Navid Saadat nsaadat@gmail.com 200319475328460016588 200319475328460016588 No Research Institute for Endocrine Sciences, ShahidBeheshti University of Medical Sciences, Tehran, Iran.