Irritable Bowel Syndrome
is a challenging diagnosis to make, largely because there is no single test that is diagnostic of the disorder. It falls under the broad term of "functional" bowel disorders, because there is a problem with the function, rather than the structure of the intestines. This distinction is an important one to make, as there is no "inflammation" of bowel that is involved, which is in sharp contrast to inflammatory bowel diseases (such as Crohn disease or ulcerative colitis).
Irritable Bowel Syndrome can be characterized by predominantly constipation, diarrhea
, or an alternation of the two, making it further difficult to diagnose.
It is tough to make specific recommendations without knowing what you have already been through, but there are some broad possibilities to think about. Many people with irritable bowel syndrome have food insensitivity at the same time. You may have some degree of lactose intolerance, meaning avoiding lactose, cheese, milk, and ice cream may be beneficial. Some people notice worsened symptoms after other specific foods, and you may try to modify your diet based on your own experience, as well. There are also some data to support increased consumption of soluble fiber (such as psyllium, rather than bran). Otherwise, large studies have been unable to show benefits of dietary modification for patients with irritable bowel.
Overall, IBS is a poorly understood entity without a clear cause. You can try to modify your diet based on your symptoms, and consider fiber, but there is no structural problem with your intestines that will be altered by fasting or other dietary alterations.