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Background: Probiotics are live microorganisms that have positive effects on the host when consumed in sufficient amounts. According to several studies, probiotics have beneficial effects on prevention and treatment of many diseases. The aim of this study was to review animal and human studies on the role of probiotics in reducing serum cholesterol, their mechanisms of action, and a brief explanation of functional probiotic foods. Materials and Methods: This review article focused on all papers indexed in scientific databases from 2000 to 2012 using the related keywords, including cardiovascular diseases, probiotics, and serum cholesterol. Results: Probiotics are used both in dairy and non-dairy products. Nowadays, the role of many probiotic strains in health is confirmed. From the studies done in this field, it can be inferred that probiotics through several mechanisms, such as binding cholesterol to cell walls of probiotics in intestine, conversion of cholesterol into coprostanol, production of short chain fatty acids, and deconjugation of bile acids, reduce serum cholesterol. Conclusion: Certain strains of probiotics have demonstrated cholesterol-lowering properties and others are under study. Further studies are needed to identify other mechanisms involved in lowering serum cholesterol and determine their safety

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Background: Obesity, the most common health problem, can result in the incidence of many chronic diseases. genetic and environmental factors can affect its incidence. Differences in the population of gut microbiota in lean and obese subjects and interaction between them, has led to a field of investigation about the effects of intestinal microbiota in the obesity occurrence. In the other hand, the use of functional foods has been shown positive effects in the prevention of obesity. This study was aimed to assess the differences between gut microbiota in obese and normal people, their roles in energy homeostasis and the mechanisms of probiotics and prebiotics in the management of obesity.

Materials and Methods: All articles indexed in the valid scientific data bases published between 2000 And 2014 were Searched and reviewed using probiotics, prebiotics, obesity and gut microbiota as key words and results were examined.

Results: A group of gut microbiota facilitates energy extraction from the diet that results in fat storage in adipose tissues. bacteroidetes as a residing bacterial in the gut is in fewer amount, inversely, firmicutes as another residing bacterial is in higher amount in obese people, and it changed in lean individuals, inversely. Differences in the extraction of energy in subjects were attributed to differences in the composition in gut microbiota. archaea ‌species that resident in the gut involved in energy homeostasis through increasing the ability of fermentation, electron production and removing the energy. In addition to, the probiotic and prebiotic supplements have roles in the prevention of obesity via stimulating the growth of beneficial bacteria, production of short chain fatty acids, modulating the secretion of hormones involved in energy homeostasis.

Conclusion: Further studies are needed to identify the specific probiotic bacteria and other effective functional foods in management of obesity.