A ton of salid. A gallon of romaine lettace has less than 20 grams of digestible carbs, and can supply a great deal of fiber. Nutts are a good source. Macadeamia nutts and walnuts are very low carb, and contain a lot of fiber. One cup of shelled walnutts contains only 7 grams of carbs that you can absorb, but contains 12 grams of fiber.