This is a video from 2011 TEDxManhattan Fellow Stefani Bardin. In the video, they compared how the body digests a processed food meal vs whole foods meal.
The results show how the body inherently has a much harder time breaking down the processed meal. Where as the whole foods meal breaks down with much more ease. The struggle to break down the first meal is what leads to gastrointestinal issues, the sleeping feeling you get sometimes after eating, and what I suspect contributes to aggregating diseases such as Crohn’s disease.