## 3 Results  
### Effects of the Mediterranean Diet on the Intestinal Microbiome, Obesity, and Metabolic Syndrome  
In a recent case-control study, 18 overweight obese subjects and 18 normal-weight volunteers followed a Mediterranean diet enriched with 40 g/day high-quality extra virgin olive oil (HQ-EVOO) for 3 months. All subjects received a typical Mediterranean diet (55-60% carbohydrates, 25-30% polyunsaturated and monounsaturated fats, 15-20% proteins) and cases followed a low-calorie Mediterranean diet (1552 \(\pm\) 160 Kcal). Both cases and controls consumed 40 g/day of HQ-EVOO for 3 months as the exclusive cooking and dressing fat. Anthropometric assessments, questionnaires, blood, and fecal samples were collected at the beginning and after 3 months of the Mediterranean diet rich in HQ-EVOO (T1). There was a significant reduction in inflammation and oxidative stress in both controls and cases, while IL-10 and adiponectin were increased in the cases. Beneficial gut bacteria, mostly _Lactobacillus_ strains, increased in the cases after a Mediterranean diet enriched with HQ-EVOO [23]. In another study, 82 healthy overweight and obese subjects that followed a sedentary lifestyle, participated in a parallel 8-week randomized controlled trial. Forty-three participants consumed a Mediterranean diet and 39 consumed their regular diet. Individual conformity to the protocol was estimated every 2 weeks by self-recorded 7-day food diaries and physical activity questionnaires. Visits and sample collections were carried out at baseline, 4 weeks and 8 weeks. The dietary modifications in the group that followed the Mediterranean diet led to a reduction in carnitine in plasma and urine, as well as a decrease in plasma cholesterol, an increase in insulin sensitivity and a reshaping of gut microbiome composition. A significant inverse correlation was observed between the variations in gut microbial gene abundance and inflammatory status estimated by serum C-reactive protein (CRP) variations. During the increasing Mediterranean diet adherence phase, _Ruthenium lactatformans_, _Flavourifractor plaulti_, _Parobacteroides merdae_, _Ruminococcus torques_ and _Ruminococcus grausus_ were significantly reduced [24]. The latter species are proinflammatory species due to the secretion of a polysaccharide that induces tumor necrosis factor alpha (TNF-a) [25]. In parallel, there was an increase in potentially beneficial species, including the fiber-degrading _F. prausnitzii_, Roseburia and members of the Clostrtiales and Lachospiraceae taxa, related to the butyrate precursor functional pathways. These potentially beneficial species were previously documented for their anti- inflammatory properties [26] and were found to be increased in the participants who consumed the Mediterranean diet [24]. In a 12-week single-arm pilot trial, nine participants followed nutritional counseling sessions according to a Mediterranean diet. The participants were men and women aged 40-80 years, non-smokers, with type II diabetes. Biochemical parameters, body composition, gut microbiota, and blood pressure were measured at the beginning of the study, 4 weeks, and 12 weeks after the intervention. Bacterial diversity and richness were increased. Bacterial variety was negatively associated with glycated hemoglobin (HbA1c) and bacterial abundance was negatively correlated with fasting glucose levels. An increase in the Prevotella/Bacteroides ratio was observed and there was a reduction in HbA1c. An evaluation of Alkaline phosphatase activity in fecal samples was conducted as a parameter of intestinal permeability and inflammation; this was positively related to bacterial diversity and negatively correlated with HbA1c [27]. Consuming a Mediterranean diet increased the activity of intestinal ALP, while the activity of this enzyme induced an increase in bacterial richness and a lowering of HbA1c.