When it comes to bread, it is not safe to assume that all brown bread is full of fiber. There are many breads out there that are really white bread darkened with caramel coloring or molasses, and neither of those ingredients offer much in the way of fiber.
You need to read the nutrition label and the list of ingredients to make sure you are getting whole-grain bread. When reading labels look for the words: whole wheat, whole grain, whole mill, whole oat, or whole barley. The keyword is "whole." Also check the fiber content of the bread and go for the highest amount possible. I like my sliced bread to contain four grams of fiber per slice, but will settle for three grams, especially if the sugar content is low.
Remember that you should be eating 30 grams of fiber daily. Just think, at four grams a slice, a sandwich can get you 25 percent of the way there.