This shows a cross-section:

There are microvilli that are essentially pleats in the gut that further increase the area of the microvilli. They are presented here on a mm scale. The total surface area in now on the order of ~100 fold that of a smooth tube.

This means that every nutrient molecule that is saved in passage reduces additional risky foraging. Every molecule that is lost in passage requires the animal to go out into the world to do more foraging. This is a tremendously efficient mechanism. The regulatory schemes must also be constrained to optimize energy use.

Since all of these basic processes must approach optimality (involving physics and chemistry for packing in space). we should think twice about tweaking them with drugs. They are really in good shape. Tweaking them is often going to mess things up.

The next point about homeostasis that is wrong concern the parameters of the body. They are not constant. They vary continuously. Variations are made not to correct errors; but are made in response to predicted needs. The idea is to provides just enough of whatever parameter that you are regulating and just in time. This is the way to run an assembly line. This is Toyota’s slogan: just enough. Just in time.