Many people think ulcers are directly caused by hunger. They assume that skipping meals or staying too long without food is what “creates” an ulcer. The truth is quite different. Hunger does not cause ulcers. What it does is make the pain of an existing ulcer more noticeable and more uncomfortable.

https://www.u-health.org/post/hunger-doesn-t-cause-ulcer-an-addendum-to-how-being-a-student-can-cause-you-ulcer