As far as I know, yeast helps the dough rise by eating away some of the sugar in the flour. But if we make low-carb bread (with, say, soya flour), yeast has nothing to eat and the bread will not rise. One solution might be to use baking powder, but then our bread has a cake-like texture. Do you have any suggestions? Thanks in advance. 
As Bikeboy said, sugar will hasten the process, but yeast has enzymes that break down the starch to get to the sugar components.  If it has starch in it, yeast will eventually persevere and the dough will rise. It doesn't have to be wheat starch, but the yeasts we use commonly are used to working on wheat or barley flour. They will adapt to other starches. It may be better to make these breads on the sourdough principle, once you persuade a yeast to work.  If it takes longer than usual, you need to have patience ...  