Do you eat anything with wheat flour?
Bread and cheese and milk are on the top of the list of foods that slow down the time it takes for the food to pass through the intestines.
It also makes for very dry and hard poop.
Total elimination of all wheat and cheese helps to most people.
A lot of water and fruits like plums and apples, vegetables like carrots, onions, parsley, cucumbers, tomatoes, green salads, are foods that can increase the speed and can make it easier to poop as it creates a softer poop.
One day of change in diet is not enough.
It can take several days of a new diet to re-establish a new bowel flora and a new kind of poop.
Squatting on the toilet can also help poop, instead of sitting on the toilet.