My experience has always been that during the ebb of a Crohn's flare, carbohydrates pass with the least residual damage. In the long term, however, carbohydrates are increasingly the spotlighted culprit of havoc-wreaking; and not solely by way of Klebsiella.
I've flirted with the Paleolithic (or, SCD) diet before; before diving headlong into this most recent flare (2.5 mos, and counting), I was balancing quite nicely in a Me Friendly version of the Paleo diet. Because I had only been doing so for several days before The Fall, and because my gastrointestinal condition had been sloughing downhill for almost a year, I wasn't able to give the diet a legitimate chance.
Now that I'm working on climbing out of this crevice, however, I'm trying to shift my current selection of solid foods away from Carbo Loaded and into Paleocentric orbit. My Me Friendly version of this was additionally limiting the red meats (fats), nuts (fats and allergies) and very fibrous vegetables (obstruction).
What I aim to do nearly without:
dairy (no brainer)
sugar (no brainer)
salt (no brainer)
grains (categorically similar to dairy in terms of damage, but I don't seem to have a gluten problem so we'll keep those with low glycemic indices)
legumes (see above; I could never entirely eliminate legumes...)
red meat (fats)
nuts (fats and allergies)
berries (seeds)... These last three are part of the "Do Consume" stipulation of the Paleo/SCD diets; alas, knowing that they destroy me I cannot invite mucosal carnage.
What I aim to tolerate:
poultry and fish
fruit (without pulp or small seeds)
root vegetables (non-stringy)
fermented foods (this should be interesting)
other foods with low glycemic indices
I'm typically quite skeptical of the hardcore diet reversions that try to re-plant us in the days before preservatives and cooking. Most of the diets that come recommended with Crohn's are pre-processing, or Paleolithic era (Dr. Balzer summarizes this nicely). Atkin's, Raw Food, SCD-- they're all based on caveman diets. And that's fine, except that we haven't been Cro-Magnon for 20,000 years. Very, very few proponents of these diets take into consideration the evolution that has occurred in the human gut during the gap between then and now (not to mention the inherent shift in caloric intake). I'm truly at a loss as to why.
It's sort of like how Western culture touts that if we all ate three rice-based meals a day -- heavy on the salts and carbs, mind you -- we'd all sport Asian slender, low cholesterol and have beautiful creamy skin. This false-cause fallacy forgets that one can train the body to produce the proper enzymes to accommodate such an adjustment, but it's not all about enzymes... there are genes involved (Ley et al 2008; Bengmark 1998). The anthropologists argue that we currently evolve too rapidly for these genetic influences to accommodate (Kligler & Lee 2004); my position continues to be that epigenetics and post-translational modifications negate that stance. The microbes that inhabit our gut and help us process food have co-evolved with us, any may respond to a dynamic change in diet either positively or negatively depending on your physiology and genetic predisposition.
My bias is moderation. Unless you have a predictable or distinguishable allergy, it is usually not helpful to eliminate something from your diet entirely. Gluten, yes. Dairy, okay. Carbohydrates, not so much. Fruit, definitely not so much. I can't do a hardcore Paleolithic or SCD diet because I have never been able to limit my diet that strictly for an extended time without invoking a flare -- which is something else the caveman diet prognosticators tend to neglect; the importance of variety. Variety is why people on the Homeopathic route take Probiotics.
I also have a resistance to thoroughly processed foods heavy on the preservatives, sugars and salts; this resistance escalates to phobia when I am on PPR. The Ley group argues that the evolution of agriculture and cooking didn't have an appreciable effect on our Gut Flora -- that the preparation of otherwise inedible grains which are the primary sustenance of our microbiotic friends did not significantly encourage their co-evolution. Others suggest that these new tools were the paradigm shift that brought about an exponential predisposition to gastrointestinal disorders. My bias aside, there is more sufficient evidence for the latter case from genetic, microbiological, anthropological and other fields (Cordain et al 2005; Wrangham et al 1999).
So we'll see how this unfolds.