Digestion is a coordinated process. Food is broken down, nutrients are absorbed, and the remaining material moves through the digestive tract. Gut microbes also ferment some compounds that escape digestion earlier in the process.
Fermentation is not automatically a problem. It is normal microbial activity and can produce compounds used by the body. The effects depend on where fermentation occurs, the amount and type of food, individual sensitivity and health context.
Bloating or discomfort can have many causes. A persistent change in bowel habits, severe pain, blood in stool or unexplained weight loss needs timely medical assessment.