Gut bacteria are considered important because it is connected to our digestion and secrete good compounds for human absorption. However, some behaviors could cause the individual have a significant gut bacteria composition, for example, eat only few foods, long-term overnight, non-fiber diet and so on.
For those who do not eat different types of foods, they would have less variety of gut bacteria categories, because the food is also the energy resource of bacteria, when the food is limited to few categories, other bacteria that do not utilize that foods would decrease even extinct in the gut. Stay overnight will increase the bacteria proportion that related to obesity or diabetes. Fiber eating could increase the gut activity to avoid obesity.