Gas forms in your body from two sources: from the air you swallow and from the breakdown of undigested food.  When food is being digested in the small intestine, a lack of enzymes can keep some carbohydrates from being digested and absorbed.  The undigested carbohydrates then travel to the large intestine, where they’re broken down into hydrogen, carbon dioxide and, sometimes, methane gas.  Watch this video to get more answers to your questions about gas!