Do people who fast and dont eat all day get gastritis/ulcer? as stomach produces acid in anticipation of food. can it be the sole cause for it.

Some basics: The stomach parietal cells create acid in quantities needed to prepare food to enter the small intestine. There is always a baseline acid production/acid environment. The food slurry must reach an acid pH or the digestive enzymes will not be effective. Gastritis can/is triggered by a variety of issues including infection. Infection is also a co-factor in ulcer production. Fasting is not a factor.