Chemically induced intermittent fasting.
The negative side effect of gastroparesis is definitely present, but it's not quite as extreme as you're suggesting here.
A lot of the recent scholarship trying to figure out how GLP1 drugs actually work is more focused on GLP1 receptors in the brain as well. Good write up on it over at the Atlantic:
https://web.archive.org/web/20240305193736/https://www.theat...