I faintly seem to remember something like this that was reportedly created for space flight, a source of nourishment without much fiber to expell (probably handy in space! <img src="/images/graemlins/smile.gif" alt="" />).

It would probably be better than nothing, although they do mention it as a supplement to other food you might be finding (greens, bugs, fish, etc).

Although you CAN go without food for quite a while (as long as you have water), those who have done it say it's not something to relish. And there are probably side-effects to even temporary starvation that would be undesirable if you were having to exert considerable effort to work your way out of a bad situation.

Sue