Why do you have bad gas after eating?

Answer 1

Bacteria living in your large intestine (this is normal, everyone has them and you would die without them) begin breaking down indigestible dietary fiber in the food you just ate. This dietary fiber is composed of very long chain complex carbohydrates (that mammals cannot digest), the bacteria break it down to simple sugars which they use as food (but you also absorb some of these simple sugars released by the bacteria so both of you benefit). But in the process of breaking down this dietary fiber the bacteria also release gasses as waste, a mixture of methane, carbon dioxide, and hydrogen sulfide. And that gives you gas.

Products like Bean-o contain an enzyme called alpha-galactosidase (derived from a fungus) that can digest this dietary fiber partially and acts before the food reaches the large intestine where these bacteria live. This reduces the problem significantly.

Products like Gas-x contain a mild detergent called simethicone that causes the gas bubbles to collapse forming much tinnier bubbles. While this does not eliminate the gas it stops the bloated feeling and pressure pain caused by the large bubbles that sometimes form.

Answer 2

That you need the toilet right away...