Dietary Fiber with Crunchy Texture I'm looking for a dietary fiber or a mix of dietary fibers (and other ingredients which act like dietary fibers such as sugar alcohols) with really low (even zero) food calories that I can create a crunchy (as in chips) or crusty (as in bread) texture. 

Please think of molecular level fibers not as in fiber-rich food. For example a common dietary fiber is Inulin (which is a fructan) and can be used as a sweetener. Another one is Glucomannan which is used as a thickener and a gelling-agent. Both of these have no calories.

I thought of using Isomalt, which to some extent acts like a dietary fiber, to make hard candy, but I think it's not going to be as low calory as I want since it's just half the calories of sugar or flour. I'm looking for recommendations to achieve such a texture, which could be considered suitable for a calorie controlled diet.

As a response to the close requests:


I'm not asking for a recipe, the question is about ingredients and techniques
I don't think it's broad for the following reasons:


I'm asking for a very specific texture and how to achieve it.
I don't know of any combination that could result in such a texture with low calories. Think of a combination before voting close for this reason (better yet, write it on the comments :))
I want to explain few things about dietary fiber.

Soluble fiber is not digested in the small intestine but it can be fermented in the large intestine by normal intestinal bacteria into nutrients (which are absorbed) and gases. Soluble fiber can have 1-3 Cal/g (sugar, starch and other digestible carbohydrates have 4 Cal/g) and can cause bloating and gas. For exact calorie value of the exact fiber, you need to check the Nutrition Facts labels. Or you can check in MyFitnessPal, which says that, for example, 1 tsp of glucomannan has 10 Calories.

Examples of soluble fiber (naturally present or added to foods):


Fructooligosaccharides (FOS), inulin, galacto-oligosaccharides (GOS), isomalto-oligosaccharides (IMO), lactosucrose, mannan-oligosaccharides (MOS)
Beta-glucan (in whole barley and oats)
Pectin (in apples, bananas...)
Gums: acacia (arabic), beta-mannan, carob (locust bean), fenugreek, glucomannan (konjac), karaya, tragacanth, guar, tara gum
Resistant starches (in potatoes)
Algae and seaweeds agar, alginate, carrageenan
Other: arabynoxylan 


From the digestion viewpoint, sugar alcohols (isomalt, maltitol, mannitol, sorbitol, xylitol) are similar to soluble fiber; they have ~2 Cal/g, except from erythritol, which has close to zero calories. 

Insoluble fiber is not digested in the small intestine and not fermented in the large intestine, so it has practically zero calories and does not cause gas.

Examples of insoluble fiber:


Cellulose (in whole grains, in cabbage family of vegetables, in fruit skins...), hemicellulose and methylcellulose (as an added thickener)
Lignin (in wheat bran, flaxseed...)


Many of these fibers are available in markets. Before buying, find the info about "relative sweetness."

Here's the source with links to all individual fibers.

Here's an one page comprehensive article about Texture modifying agents, such as gelatin, corn starch, pectin, guar gum, methylcellulose, etc.