Assume the smoothies have the same nutrient profile as a regular diet. Like if you drank runny mashed potatoes and protein powder to simulate a normal food intake.
If you do poop because of the nutrients, is there a healthy diet at which waste products are no longer left in the intestine to turn into poop?
Drag has no intention of doing this, drag is just curious about the science.
Tangentially related, but when I switched my cat from commercial cat food to a raw chicken (w/ supplements) diet, her poops went from very bulky once a day, to shrivelled poops every-other day.
The amount of water in the chicken, and the lack of bulking ingredients made a huge difference.