Low in fiber. No grains (not just gluten-free), not even rice or corn. No starches, including potatoes. No processed sugars. Can't have most beans, and the ones I can have have to be pre-soaked properly. No soy except for soy lecithin. No lactose, but aged cheeses are fine. No gums, such as xanthan gum, guar gum, etc. No maltodextrin or other grain derivatives. No agave nectar, maple, molasses, or other sweeteners other than fruit juice, honey, or stevia. No sugar alcohols like erythritol, xylitol, sorbitol., etc. All meats are fine, but I avoid red meat as a general rule. Nuts and eggs are okay.

And that probably doesn't cover all of it. Almost any processed food or restaurant menu item has at least one problem item. :/