Why is fat digestion considered limited in the mouth and stomach compared with the small intestine?

Because lingual and gastric lipases denature at neutral pH encountered in the small intestine, so they are only active after bile salts decrease the pH again to re-activate them.

Because the stomach actively absorbs most fatty acids there, leaving little substrate for intestinal digestion; the small intestine is primarily responsible for water and electrolyte handling rather than lipid processing.

Because mechanical peristalsis in the stomach completely prevents enzyme–substrate contact for lipases, and pancreatic enzymes are synthesized in the mouth to be delivered via saliva later into the colon.

Because lingual and gastric lipases contribute only modest hydrolysis and effective large-droplet emulsification requires bile released into the small intestine for pancreatic lipases to access substrates efficiently.