Causes of a bloated stomach. Stomach bloating refers to the abdominal swelling that occurs as a result of excess gas and fluids that have accumulated in the abdomen, causing the waist’s diameter to increase.There are several reasons why this occurs and the most common are:tomach bloating refers to the abdominal swelling that occurs as a result of excess gas and fluids that have accumulated in the abdomen, causing the waist’s diameter to increase. There are several reasons why this occurs and the most common are: