Your food either has a high or a low digestability. Let me explain.
Digestability is a word I created to describe your food's digestive efficiency. Often we give little or no thought to our food's transit time or about how our food gets through the digestive tract. This is often a good sign since not feeling any symptoms can be perceived as a sign of health. We often don't think about our food's transit time until we're constipated or getting some other symptom.
Your food has a high digestability if it is plant-based. Essentially, fruits, vegetables, and legumes have high digestibility. Usually high digestability foods have a high water content (fruits and vegetables), and are high in fiber, minerals, vitamins, and other nutrients. They also move quickly and efficiently through the digestive tract.
Your food has a low digestability if it takes a long time to get through the digestive tract. These foods usually have longer transit times -- sometimes one to three days. Low digestability includes fat, (which takes the longest to digest) animal proteins, and fast and processed foods that are low in fiber. It is not uncommon for a very low-fiber, very high-fat, and very high-calorie meal to remain unmoved in the digestive tract for more than two days. This stoppage is conducive to both constipation and chronic disease.
That being said, how long transit time is for food to digest is individual and not only a function of the food. Your body's ability to digest is also a function of your overall health, your degree of physical activity, and your overall muscle tone. It goes without saying that humans who have a laxative habit need to correct the amount of muscle tone needed to help move their food through the digestive tract--a process known as peristalsis. Still, eating foods that have high digestability as well as increasing your amount of activity, is usually an effective natural cure to end symptoms of constipation expediently.