Fermenting foods in the colon produce hydrogen and methane as well as carbon dioxide and oxygen. The unpleasant odor of some flatus is the result of trace gases, such as hydrogen sulfide, indole, and skatole, which are produced when foods decompose in the colon. Eating a lot of fatty foods can cause bloating and discomfort because the fat delays stomach emptying, allowing gas to build up. This problem can be avoided by eating less fatty meals. The feeling of bloating in the abdomen may increase during the day and become most severe after a large meal.
Many people think the bloated feeling after eating is caused by large amounts of gas.
Researchers, however, have not found any connection between this symptom and the total amount of gas in the abdomen. Gas in the upper abdomen often is relieved by belching. Sometimes people try to swallow air to make themselves belch. This doesn't work, however, because it only adds to the amount of gas in the stomach and does not reduce the discomfort. Gas can collect anywhere in the lower intestine.