Even so, keto followers may experience a rise in LDL cholesterol, sometimes called “bad” cholesterol because too much of it can lead to a buildup of plaque in the arteries, which can increase the risk of heart disease. And that’s where fiber can help. However, many high-fiber foods, like beans, fruits, vegetables, nuts, seeds, and whole grains, are also high in carbs, so they're limited on the keto diet.
Taken together, previous research in combination with our lab’s current research may argue that IMOs should not be classified as a “true fiber.” Rather, IMOs should be viewed as a very low glycemic carbohydrate source, much like steel cut oats. In essence, if you see a low-carb snack that has 20 grams of IMO fiber, it is likely that approximately 16 grams of this fiber will act as a slow-digesting carb, and four grams will act as an indigestible fiber. Those who are on a ketogenic diet should be aware of these fibers and proceed with caution when consuming them in large amounts, as they could raise both blood glucose and insulin levels. A more ketogenic-friendly fiber is SCF, which has been demonstrated to act as more of a true fiber. Additionally, SCF is very tolerable in the gut despite its profound prebiotic activity. It is important to keep in mind that everyone is metabolically different, so if you are consuming food items with these fibers in them, be sure to monitor blood glucose and ketone readings to find how each of these fibers personally affects you.

Lastly, one of the advertised benefits of IMO is possible prebiotic activity. Prebiotics are critical, as they feed the beneficial bacteria in our digestive system, specifically in the large intestine. These bacteria have several amazing functions, such as lowering body fat, improving insulin sensitivity, and lowering depression. Two “gold standard” prebiotics in the industry are inulin and fructooligosaccharides (FOS). Inulin and FOS are non-digestible carbohydrates that robustly increase beneficial bacteria. The challenge, however, is that both inulin and FOS, due to their rapid digestibility by intestinal bacteria, result in low gastric tolerance, and, ultimately, gastric distress. Additionally, inulin and FOS, when added to protein bars or other goods, may degrade over time into individual sugar units. Regardless, one study comparing inulin to IMOs, found that the prebiotic activity in inulin is 14 times greater than that of IMOs.[4] This is logical because, as you recall from above, approximately 70% to 90% of IMOs are digested. As such, only a small portion of these prebiotic fibers make it to the large intestine, in which two out of three studies have demonstrated that this small portion may indeed have some prebiotic effects.