Gut microbiota and physical exercise in obesity and diabetes – A systematic review

•Physical exercise as a beneficial gut microbiota modulator in metabolic diseases.•Physical exercise as an alternative therapy for metabolic diseases via gut microbiota.•Physical exercise may modulate the gut bacteria diversity and abundance in obesity.•Physical exercise may reduce metabolic endotoxemia markers in type 2 diabetes.•The benefits of exercise on gut microbiota need to be proved by well-designed trials.