In contrast insoluble fiber, which does not dissolve in water, is inert to digestive enzymes in your upper gastrointestinal tract. While some forms of insoluble fiber (like resistant starch) can ferment in your colon, most insoluble fiber moves through your digestive system relatively unchanged, absorbing water as it goes, eventually adding bulk to your stool and easing your bowel movements.
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.
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. 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.
If you’ve been following a keto diet then you know that it takes a bit of time to get into ketosis. Ketosis is the state in which your body uses ketones, which are created during the breakdown of fats in the liver, as a fuel source to give you energy. If you eat carbs then your body will use glucose that comes from the carbs as the main source of fuel.
Skimping on fiber isn’t good for your digestive health, as it feeds the good bacteria in your GI tract, something that benefits you beyond adequate bowel movements. “The digestive tract is where your body’s second brain is, and it’s home to the majority of your immune system,” says Elia. “If you’re following keto, it should be one of your biggest priorities to make sure you get adequate fiber to keep your gut healthy and happy,” she adds. And, she notes, high-fat diets slow digestion and decrease GI motility, so it’s especially important to get enough.