This explains how sugars and fast carbs can be healthy https://youtu.be/n28W4AmvMDE?si=xEx29eVFgDEy2ktW

Tldr; highly processed food looses vitamins(micro nutrient starvation) and starch/fiber are needed to slow absorption until it gets to bacteria producing drugs(barbiturate and precursors to neuromediators including), and give signals over vagus nerve to head. May be summary of few books from me too. Do not recall. Add on top chewing fibery food takes time, feeling full starts earlier of being full, and saliva ferments help to digest either.