There are different bacteria present in our body naturally some of which are Friendly bacteria and promote health in your body by producing nutrients such as vitamins. These bacteria also help us digest the undigested fiber. The imbalance between bacteria such as Bacteroides and Firmicutes leads a person to gain weight, especially abdomen fat. It has been observed that people with different weight possess different number count of the healthy bacteria in their gut flora. Increased number of Firmicutes in comparison to the decreased number of Bacteroides can affect your digestive system, weakens your immune system and both of these reason leads to weight gain. By making small changes in your diet and activity you can regulate the number of good and bad bacteria in your body. Eating foods that contain active microorganisms or taking probiotics may help you to lose weight faster.