Over the past 20 years or so, gut health has become a bit of a buzzword. But what exactly is gut health and what is a gut? The definition of the gut is a tube that connects the mouth to the anus which is the stomach digestive system that passes out anything that our bodies do not digest. However, the gut as a whole is not that simple. The gut has a lining that has the surface area of 400 square meters and uses roughly 2 times the amount of energy as the brain in order to function properly.