Why does a person get gassy and bloated when they have diahrea?

Fermentation . . .: Not everyone who has diarrhea will feel gassy ; bloated. Some will complain of crampy pain, often as a result of infection. The gassy bloated sensation may be due to poor digestion of nutrients, allowing bacteria to essentially ferment nutrient causing gas. Lactose, commonly found in dairy products, is a good example of possibly causing just such a diarrhea. Beans can also cause similar symptoms.