When we decide to move from one diet to another, it is important to make the change slowly over a period of one to two weeks. It may not seem like a big deal to move from omnivore to vegetarian, or processed food to whole food, or elect to dramatically increase fats while reducing protein, but the pancreas and gallbladder, the two organs responsible for making the enzymes needed to digest the food you eat, will be unprepared to handle the initial change. Often a one time digestive discomfort is taken as a reason to not eat the food again, when all that is needed is a slower ramping up in quantity over time and perhaps a little digestive support.
Regardless of whether you are increasing fat, or adding meat to an otherwise vegetarian diet, a good way is to begin by adding in single bites or teaspoons. One bite of chicken or fish, or one teaspoon of coconut oil, for example. The next day or so, if no digestive discomfort presents itself, increase again by another bite or another teaspoon. Each day, the pancreas and gallbladder will become aware of the greater need for different enzymes and begin to adjust accordingly.
The older we become, the less productive our pancreas and gallbladder can become, so it may be necessary at some point to use supplemental digestive enzymes every time you eat, or for heavier meals that include more fat and protein. Whole food has many of its own enzymes, so you may find that just eating real food (vs. processed and fast) dramatically improves your digestion and comfort after meals.
Be patient and kind to your body.