Obesity is a major public health concern, caused by a combination of increased consumption of energy-dense foods and reduced physical activity, with contributions from host genetics, environment, and adipose tissue inflammation. In recent years, the gut microbiome has also been found to be implicated and augmented research in mice and humans have attributed to it both the manifestation and/or exacerbation of this major epidemic and vice versa. At the experimental level, analysis of fecal samples revealed a potential link between obesity and alterations in the gut flora (drop in Bacteroidetes and increase in Firmicutes), the specific gut microbiome being associated with the obese phenotype. Conventionally raised mice were found to have over 40% more total body fat compared with those raised under germ-free conditions, while conventionalization of germ-free mice resulted in a significant increase in total body fat. Similarly, the sparse data in humans supports the fact that fat storage is favoured by the presence of the gut microbiota, through a multifaceted mechanism. Efforts to identify new therapeutic strategies to modulate gut microbiota would be of high priority for public health, and to date, probiotics and/or prebiotics seem to be the most effective tools. 1. Introduction Obesity is a major public health concern, threatening both the industrialized and the developing countries, largely in parallel to the adoption of a “modern”/Western-type lifestyle. It results from a long-term disbalance between energy intake and expenditure, that is, increased consumption of more energy-dense, nutrient-poor foods containing high levels of sugar and saturated fats in combination with reduced physical activity [1]. However, the mechanisms underlying obesity seem to be far from the long-held belief in caloric intake and lifestyle factors. It is becoming evident that obesity and its causes are significantly more complex than previously thought, with contributions from host genetics, environment, diet and lifestyle, and systemic and adipose tissue inflammation [2]. Obesity is now characterized by a cluster of important chronic metabolic disorders, including insulin resistance, type 2 diabetes, fatty liver disease, atherosclerosis, hypertension, and hypercholesterolemia, and by a low grade of systemic inflammation [3], being the cause of exacerbation of all the above and leading to increased morbidity and mortality. Moreover, obesity is detrimental to the quality of life as a whole and implies high health costs as a consequence of its associated morbidities. In recent
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