Low fiber and low residue diets are not really the same thing. I guess they are like rectangles and squares: a low residue thing is probably low fiber, but a low fiber thing is not necessarily low residue. For example, fruits: a lot of them hardly have any fiber, but are high residue.
You can know something is high fiber by just reading the side of the container or googling it. In general, anything with 2 grams are less is considered low fiber.
Figuring out if something is low residue is where it gets a little tricky. You kind of have to use common sense
. High residue foods are basically any foods that could potentially scrape up your insides. These "scrapy" foods include skins of fruits, nuts, berries, seeds, corn meal, that sort of thing. Basically, my rule of thumb is if you can see it on the other end, don't eat it! XD
For me, high residue foods TOTALLY mess me up. If I eat popcorn, I can guarantee that I will be flaring within the next few days. Which kind of sucks, because I love popcorn! It took me like a decade to figure that one out, and I felt like such a dummy when I did
. I could not figure out why I always seemed to get sick after going to the movies. Other foods like butter and greasy stuff do not actually bother me much, or at all, usually. So, I guess it depends on the person to an extent. But I would definitely recommend avoiding high residue foods when you have IBD, especially if you are flaring.