Although the link between gut microbiota and obesity is increasingly reported, the pathophysiological mechanisms and clinical outcomes are still under debate. This overview of human and animal data addresses several pathophysiologic mechanisms, dietary habits, exercise and probiotic and symbiotic supplementation in the fields of gut microbiota and obesity. Overall, obesity impairs gut microbiota composition due to factors that may be linked to the onset of the disease, such as excessive consumption of high-energy foods, sugars and fats, as well as a low fiber intake and physical inactivity. Conversely, low-energy diets, physical exercise, and probiotic and prebiotic supplementations can enhance gut microbiota in patients with obesity, in addition to improving cardiometabolic markers. As for perspectives, further research is warranted to ascertain proper dietary manipulation, physical exercise protocols and dosing regimens of probiotics. Regarding the latter, the effects on indicators of obesity are clinically modest, and hence skepticism must be exercised.