Fermentation needs patience
Gas can appear when microbes ferment fibre. That does not automatically mean something is wrong. Fermentation produces acids and gases, and the gut may need time to adapt when fibre intake increases.
The problem is speed. A sudden jump from a low-fibre diet to a large dose of highly fermentable fibre can feel rough. Bloating, cramps, loose stools, or constipation may mean the change is too aggressive, water is too low, or the fibre type does not suit the person. A more practical pattern is gradual: start with familiar foods, increase water, build consistency, and treat tolerance as useful feedback.