I just saw this on our local news - new product that is an all natural fat replacement used as partial fat replacements in tested recipes such as cake, chicken salad, etc. Recipe for cake where the product was used as a partial substitute (50/50, I think) for the butter was reduced in fat/calorie content by almost 1/2; chicken salad where the product was used (75/25, I think) was reduced in fat/calorie content by more than 1/2. Evidently, taste testers couldn't tell the difference in taste/texture, etc. in the products with/without the replacement.
So far, only available on their website, and not cheap -
for more information.
I would need to know the source(s) of the 'insoluble plant fiber'
could be wierd. But the idea seems interesting.