en Nutrition Nutrition Original Research Original Research <strong>Background: </strong>Metabolically healthy obese (MHO) individuals appear to be protected or more resistant to the progression of obesity-related metabolic disorders. Hormonal regulation associated with adipose or muscular tissues such as irisin and leptin may facilitate the healthy metabolic profile of MHO cases. In this case-control study, the differences between serum level of irisin was investigated in metabolically unhealthy obese (MUO) and metabolically healthy obese (MHO) individuals.<br> &nbsp;&nbsp; <strong>Methods:</strong> The study participants included obese individuals with metabolic syndrome (MetS) (n=51) and 2 control groups that included weight matched cases without MetS (n=51) and normal weight cases without MetS (n=51). Diagnosis of MetS was made based on the Adult Treatment Panel III (ATPIII) criteria. Serum levels of leptin and irisin were determined by enzyme-linked immune-sorbent assay (ELISA) kit. Receiver Operator Characteristic (ROC) curve, multiple linear regression, and one-way ANOVA analysis were used in SPSS 16 software. Significant level was set at 0.05.<br> &nbsp;&nbsp; <strong>Results:</strong> Based on the statistical analysis, serum levels of irisin were 2.91&plusmn;1.6, 3.14&plusmn;1.4, and 4.47&plusmn;3.23 (ng/mL) in MUO, MHO, and nonobese metabolically healthy participants, respectively (P = 0.001). Also, serum levels of leptin were 14.06&plusmn;12.4, 11.2&plusmn;9.3, and 7.09&plusmn;7.1 (ng/mL) in MUO, MHO, and nonobese metabolically healthy cases, respectively (p=0.002). After adjusting for demographic variables, a significant association was found between irisin and study groups (&beta; = 0.77, P = 0.001), weight (&beta;=-0.03, p=0.014), BMI (&beta;=-0.11, p=0.006), TG (&beta;=-0.003, p=0.025), fat mass (&beta;=-0.04, p=0.046), and fat free mass (&beta;=0.08, p=0.014).<br> &nbsp;&nbsp; <strong>Conclusion:</strong> Obese patients with/without MetS had lower level of irisin than normal weight participants. Irisin, Obesity, Metabolic syndrome, Leptin 324 330 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-4648-2&slc_lang=en&sid=1 Somaye Yosaee S_yousai2006@yahoo.com 200319475328460063951 200319475328460063951 No Department of Nutrition Sciences, School of Health, & Department of Nutrition, Emam Reza Teaching Hospital, Larestan University of Medical Sciences, Larestan, Iran Reyhane Basirat r.basirat@yahoo.com 200319475328460063952 200319475328460063952 No Nutrition Research Center, Department of Clinical Nutrition, School of Nutrition and Food Sciences, Shiraz University of Medical Sciences, Shiraz, Iran Abdolhamid Hamidi Hamidhamidi_e@yahoo.com 200319475328460063953 200319475328460063953 No Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran Alireza Esteghamati esteghamati@tums.ac.ir 200319475328460063954 200319475328460063954 No Endocrinology and Metabolism Research Center (EMRC), Vali-Asr Hospital, Tehran University of Medical Sciences, Tehran, Iran Mahmoud Khodadost mahmodkhodadost@yahoo.com 200319475328460063955 200319475328460063955 No Department of Epidemiology, Faculty of Health, Shahid Beheshti University of Medical Sciences, & Department of Epidemiology, Faculty of Health, Iran University of Medical Sciences, Tehran, Iran Farzad Shidfar shidfar.f@iums.ac.ir 200319475328460063956 200319475328460063956 No Department of Nutritional Sciences, School of Public Health, Iran University of Medical Sciences, Tehran, Iran Vida Bitarafan bitarafanvida@gmail.com 200319475328460063957 200319475328460063957 No Adelaide Medical School and National Health and Medical Research Council of Australia (NHMRC), Center of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia Kurosh Djafarian kdjafarian@tums.ac.ir 200319475328460063958 200319475328460063958 Yes Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran