Digestion isn't just input and output. All the hollow spaces food goes (the mouth, esophagus, stomach, and intestines) are called hollow organs and guess what- each one is muscular!
They can expand (think of your belly after a holiday meal) and they can shrink back to normal.
This take muscle control, so exercise #1 is:
Let Your Digestion Empty Completely
This doesn't have to be fancy- for example, a light and easily digestible dinner that's over by 7pm like a hearty soup, then nothing till at least 7am the next day.
Give your digestive organs a break, and a chance to change sizes. Give the lymph fluid and connective tissue around your organs some space, and some fresh blood flow. And give all the tissues a chance to heal: the GI tract really has a lot of constant damage to repair, so a pause gives all this a chance to happen.
Practice Gentle, Full ROM Bends and Twists
ROM= Range of Motion
This could be yoga moves. This could be spine twists on the floor. This could be backbends supported by a door frame. This could be toe touches, no bouncing!
There are so many ways to deliberately and fully twist and bend to stretch our insides, just do it smoothly and without holding your breath.