###### Abstract  
The human gastrointestinal gut consists of about 100 trillion microorganisms, including up to 5000 different types of bacteria, as well as Archaea, Eukarya, parasites, viruses and bacteriophages that together are called the \"gut microbiome\". Changes in gut microorganism composition (dysbiosis) can cause various diseases. The present study aims to investigate if diet, and more specifically, functional foods have an impact on the intestinal microbiome, and whether the intestinal microbiome has an influence on metabolic syndrome (MetS) and obesity. This systematic review was accomplished according to PRISMA guidelines, mostly using the key words functional foods, microbiome, obesity, MetS, and Mediterranean diet. The search focused on recent scientific articles from the Pubmed, Scopus, and Google Scholar databases. Most of the studies discussed showed a potential therapeutic effect of the Mediterranean diet, which is rich in beneficial nutrients, on body weight and fat deposition, through reshaping of the gut microbiome's synthesis. This literature review showed a possible relationship between microflora metabolites, endotoxemia, obesity and MetS. The role of probiotics, prebiotics, and polyphenols in the prevention of obesity and MetS is of high importance in promoting healthy aging. The future challenge is to comprehend how different dietary patterns could regulate the gut microflora's composition and whether these changes could be long term. functional foods; microbiome; obesity; metabolic syndrome; polyphenols; prebiotics 2024202420242024202420242024202420242024202420242024202420242024202420242020242024202420242024202024202420202420202420202420202420202420202024202020202202020  
The most widespread, non-communicable diseases, such as obesity and MetS, are increasing worldwide. They are both distinguished by a state of inflammation and reshaping of the intestinal microflora [5]. The World Health Organization (WHO) defines obesity as an excessive accumulation of body fat, mainly visceral fat, which can induce health damage [9; 10; 11; 12]. Worldwide, 2.1 billion people are overweight or obese [13]. The major concern about obesity is its relationship with chronic metabolic diseases such as insulin resistance (IR), cardiovascular diseases, type II diabetes and MetS [9; 10; 14]. WHO defines MetS as a pathological condition characterized by obesity, IR, hyperlipidemia, and hypertension [14; 15]. Several studies have shown that dysbiosis leads to low-grade inflammation, obesity, and, consequently, MetS [2; 16]. Dysbiosis is a condition of imbalance between the various microorganisms in the human gut. It can be caused by hereditary factors, antibiotics, radiotherapy, chemotherapy, and age; however, it is mainly related to imbalances in nutrition, physical and psychological stress, resulting in dysregulation of the immune system [17]. Recent scientific research associates MetS with intestinal dysbiosis [14]. Intestinal dysbiosis increases intestinal permeability, which can cause the translocation of lipopolysaccharide-charide (LPS), a component of the external membrane of Gram-negative bacteria, resulting in metabolic endotoxemia, low-grade inflammation, IR, and weight gain [2; 5; 7; 10; 18; 19; 20]. The gut microbiota are considered a metabolic gateway between the external environment and the host, in terms of energy metabolism, bodyweight homeostasis and inflammation regulation. Obesity has been shown to be related to the modification of gut microbiota and obesity phenotypes and can be transmitted through gut microbiota in rodent models. Probiotic bacteria, as part of the fermented traditional functional foods of the Mediterranean diet, may contribute to reducing dysbiosis and promoting human health [16; 21]. Diet is considered a key factor for the modification of microbial gut diversity. Some food ingredients have possible beneficial effects on human health beyond the provision of basic nutritional needs, and are known as functional foods.