Final answer:
The hormone gastric inhibitory peptide is responsible for slowing gut motility by inhibiting gastric motility and acid production, thereby allowing more time for the digestion and absorption of nutrients, especially fats.
Step-by-step explanation:
The hormone responsible for slowing gut motility is known as gastric inhibitory peptide (GIP). Contrary to motilin, which accelerates gastric emptying and stimulates peristalsis, GIP plays a different role in digestive physiology.
When foods rich in fatty acids and sugars enter the small intestine, they trigger the release of GIP. This hormone's primary function is to inhibit the gastric motility and acid production, which, in turn, slows down the rate at which food exits the stomach and enters the small intestine. The purpose of this slowing mechanism is to ensure that there is sufficient time for these nutrient-dense foods to be properly digested and absorbed. As a result, GIP helps optimize the digestion process especially when dealing with high-lipid meals that require longer digestion times.
PYY is another hormone implicated in regulating gut motility, working with the enteric nervous system to adjust the contractions that propel material through the intestines. However, the direct answer to the question is the gastric inhibitory peptide.