"microbiome uses to tell the body that it is sated (namely the production of short chain fatty acids SCFA from soluble fiber in the colon"

Except that's obviously not the full story. Try to overeat on just steak. It's really hard. The satiety index of just meat is crazy high.

Which is why the weight just melts off people doing carnivore diets (which doesn't mean those diets are optimum for health, but they do help you lose weight like crazy)