How is gas formed in the body?

First of all, everyone produces gas (flatulance) despite the protestations of some people. The bacteria that resides in the large intestine actually completes the final process of digestion. This bacteria breaks down any remaining carbohydrates and proteins. The byproduct of this breakdown produces (among others) methane gas which contributes to the odor. That’s why certain types of bacteria that reside in our bodies are actually important digestive aids!