What's important is the first item in the list of ingredients. You're looking for the word whole. If it says enriched or wheat flour, it's a refined product. If this still sounds like eating sawdust, try changing your diet in stages. Start with wheat bread, then switch to whole wheat.
Some brands are milder than others.
You might even mix a teaspoon of oat bran or wheat germ into your yogurt. Drink plenty of water to keep your bowels from getting blocked. But you should try to get some fiber at every meal. Whole grains, of course, are not the only source of fiber, vitamins or complex carbohydrates. But that's food for another column.