Overweight and obesity are increasingly prevalent worldwide. These bodyweight disorders are closely related to deficiencies in the control of food intake. A potential yet unexplored mechanism to explain the loss of eating control is the interaction between the gut microbiota and the brain. The mechanisms underlying the communication between the gut microbiome and the host remain largely unexplored. These mechanisms could occur in part through small non-coding RNAs, called microRNAs (miRNAs). miRNAs regulate epigenetic mechanisms to control gene expression. Two hypotheses have been proposed: I. The interaction between the gut microbiota and the brain and its associated epigenetic changes play an important role in the overweight-related loss of eating control and metabolic imbalance. II.The composition and functionality of the gut microbiota are associated with circulating microRNAs and glycemic variability and modify the effect of physical activity on cognitive parameters and brain microstructure (R2\*). The study includes a cross-sectional design (comparison of subjects with and without obesity) to evaluate parameters associated with food addiction through validated questionnaires. The metabolic and behavioral profiles of the cohort will be characterized. The medial prefrontal cortex connectivity will be studied using functional magnetic resonance imaging (fMRI). The composition and functionality of the gut metagenome of the subjects will be analyzed in association with metabolic and behavioral parameters and imaging data. miRNAs can act as mediators of epigenomics of the effects of the metagenome that impact the brain, therefore it will be analyzed a broad profile of miRNAs circulating in plasma.