Hussien NI, Shoman AA. Effect of obesity and passive smoking on biochemical and histopathological changes in rat Liver and the protective effect of exercise. JEPonline 2013;16(4):101-111. Obesity has various effects on hepatic function. There is little information available for effects of exercise on biochemical and histopathological changes in the liver of obese rats. In addition the prevalence of cigarette smoking (CS) is increased among obese subjects, who are susceptible to develop fatty liver disease. The purpose of this study was to determine the effect of exercise and passive smoking on body mass index, serum lipid profile (LDL and HDL cholesterol), blood glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), albumin level and liver histology in rats fed high-sucrose diet. The rats were classified into 5 main groups: Group I, Control Group; Group II, High Sucrose Untrained Group Not Exposed to Passive Smoking; Group III, High Sucrose Trained Group; Group IV, High Sucrose Group Exposed to Passive Smoking; Group V, High Sucrose Trained Group Exposed to Passive Smoking. The findings from this study indicate that obesity induced by high sucrose diet caused significant increase in body mass index, serum triglycerides, total cholesterol, LDL−C, blood glucose, AST, and ALT as well as a significant decrease in albumin and serum HDL−C with significant changes in liver histology. All these effects were counteracted by exercise and were ameliorated by smoking. Preventing and treating obesity will be a key measure in preventing and controlling this epidemic of fatty liver disease.