Now we get to the really awful part: even if a person's stomach is full the
appears. This crusty minion is the guardian of the exit. It demands that things be "proper" before letting them out. Should the body withdraw O2 and glucose, when the lion is really close, the curmudgeon halts the works and, in worst case if this goes on too long, will throw a fix and cause an "everyone out of the pool" -> between the gums and past the lips, lookout world, here it comes!
It appears that the body pulls back O2 and glucose from the stomach at about 75-80% of MHR. That lets everything go to the muscles (and brain?) since getting away from the lion is far more useful than digesting what was swiped from the lion.
Since the stomach curmudgeon demands things be proper, there is potentially a problem if there are proteins and fats to handle. These "normally" have a digestion time of 2-6 hour. But if the "shut down" occurs, digestion time may last until hours after the shutdown is over! For STP, this is basically all day and into the night.
This is a huge problem: not as much because a person doesn't get the "calorie" benefit, but more because the stomach curmudgeon absolutely refuses to let anything out . The "proteins and fats" become a "cork" to stop everything! That really is everything, even water.
Imagine riding for 12 hours during a hot summer day without any water!
Not only is it not a pleasant thought, I suspect few would make the 12 hours before being found lying beside (in?) the road!
Of course, if the stomach is really full and exercise is really intense, the stomach curmudgeon may call it quits on this particular food and start punching (cramping) or just toss it out the front door, especially if it is an hour or so old. Consider macaroni salad on a hot summer day at 98.6 degrees for several hours, ugh). Just try swimming the start of a triathlon after a huge breakfast. An ugly way to !!FAIL!! (be sure to have your will updated and the charge for search&recovery paid)
The stomach doesn't actually completely shut down, it just slows to a very slow crawl. The stomach curmudgeon isn't cruel or stupid, just clever and dedicated to keeping things working.
If the stomach curmudgeon will let "properly digested" contents move on. In the later book on Fueling" I'll talk in detail about "properly digested food", the stomach curmudgeon, the Osmotic Police, and the Na+ jerk (soda jerk) and how they guard things during privations of lack of resources.