Iran Red Crescent Med J. 2018 February; 20(2):e59696. Published online 2018 January 8. doi: 10.5812/ircmj.59696. Research Article The Effects of Heated Oils Used in Fast Food Restaurants on Metabolic, Inflammatory and Oxidative Stress Markers, Blood Pressure, and Liver Histology in Sprague-Dawley Rats Saeed Ghobadi, 1 Masoumeh Akhlaghi, 1,* Maral Mokhtari, 2 and Fatemeh Mohammadian 3 1 Nutrition Research Center, School of Nutrition and Food Sciences, Shiraz University of Medical Sciences, Shiraz, IR Iran 2 Department of Pathology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, IR Iran 3 Department of Physiology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, IR Iran * Corresponding author: Masoumeh Akhlaghi, Ph.D., Assistant Professor of Nutrition, Nutrition Research Center, School of Nutrition and Food Sciences, Shiraz University of Medical Sciences, Razi Blvd, Shiraz, IR Iran. Tel: +98-7137251001-8; +98-7137257288, E-mail: msm.akhlaghi@gmail.com Received 2017 August 15; Accepted 2017 October 21. Abstract Background: Long and repeated heating causes multiple physical and chemical changes in oil, which may result in serious biolog- ical damages upon consumption. Objectives: This study investigated the effects of heated oils used in fast food restaurants on metabolic, inflammatory, and oxidative stress markers in rats. Methods: The experimental clinical study was performed during summer 2016 in Shiraz, Iran. For 13 weeks, 32 Sprague-Dawley rats received one of the four diets: Group 1: basal diet mixed with 15% w/w heated oil containing total polar compounds (TPC) = 12.5% (TPC 12.5); Group 2: basal diet with 15% unheated oil used in group 1 (control TPC 12.5); Group 3: basal diet with 15% heated oil with TPC = 35% (TPC 35); and Group 4: basal diet with 15% unheated oil used in group 3 (control TPC 35). At weeks six and 13, blood samples were collected for determination of fasting glucose, lipid profile, liver enzymes, and inflammatory and oxidative stress markers. Blood pressure was measured on the 13th week. Histopathological examination of liver slices was performed after euthanization of rats. Statistical analysis was done using the SPSS software. Results: On the 13th week, the TPC 35 group had higher plasma glucose (+40.4 mg/dL, P < 0.05), triglycerides (+13.6 mg/dL, P < 0.05), aspartate transaminase (+34.3 U/L, P < 0.05), interleukin-1β (+453 pg/L, P < 0.01), and blood pressure (+16/5 mmHg, P < 0.05) than the control and higher glucose (+59.3 ng/L, P < 0.001), aspartate transaminase (+55.5 U/L, P < 0.05), total cholesterol (+6.5 mg/dL, P < 0.05), and 8-isoprostane (+8.5 mg/dL, P < 0.05) than the values on week six. On the 6th week, Low Density Lipoprotein (LDL)- cholesterol was higher in the TPC 35 group than TPC 12.5 (+4.0 mg/dl, P < 0.05) and the level of serum malondialdehyde was higher in the TPC 35 than the control (+0.49 μmol/L, P < 0.001). On the 13th week, more histological changes were observed in rats of the heated oil groups. Conclusions: Long-term consumption of fried foods from fast food restaurants may have detrimental impact on blood pressure, serum glucose and lipids, inflammatory and oxidative stress markers, and liver histology. Keywords: Glucose, Inflammation, Lipids, Oils, Oxidative Stress, Rats 1. Background Frying is one of the most popular ways of food prepa- ration at home and in the food industry (1). In fact, it is a quick and easy method that enhances consumer satisfac- tion with color, texture, and taste of the food (2). However, at high temperatures, oil undergoes a number of physi- cal changes, including foam formation, increased viscos- ity, and darkening of color that alter oil appearance and lower quality (3). In addition to physical changes, pro- longed heating induces chemical reactions in oil, such as oxidation, hydrolysis, and polymerization (4), which pro- duce oxidized fatty acids, polar compounds, polymers, hy- droperoxides, and aldehydes (5) and upon consumption could cause serious health consequences in fried food con- sumers (6). These include increased adiposity (7), hyper- tension (8), cardiac damage (9, 10), diabetes (11), atheroscle- rosis (12), and cancer (13, 14). However, to the best of our knowledge, previously per- formed studies reported detrimental effects of oils heated under laboratory conditions (7-9, 11, 15). For instance, ad- ministration of palm oil heated five and 10 times to rats Copyright © 2018, Iranian Red Crescent Medical Journal. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.