The proof that the act of eating anything can trigger IBS symptoms is given by Heather in the explanation of the gastrocolic reflex. In these video interviews with Prof Whorwell an internationally recognized GI doc on the IFFGD gives more insights. He talks about the effects of eating and IBS in the interview "Diet, eating and IBS".
Some people feel the effects of some foods sooner or later than others. For me it is a 2-3 hours for IF and 40-70 minutes for fructose, sorbitol, FOS, etc. Fatty foods it is next day. IBS trisgger effects can occur from the time one starts eating through to the time fermentation of undigested food takes place in the colon. The range is from minutes to a day or two.
Research shows that while SF reduces gastric emptying time from the stomach to the small intestine IF doesn't. On the other hand IF decreases small intestine and colonic transit time. If you dig through the library and read some of the newsletters you may find more details.
Different foods and different fibers have different effects on different people.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS