Understanding Fiber: The Good, the Bad, and Their Impact on Your Health

Good Fiber, Bad Fiber - How The Different Types Affect You

Fiber is more than just a buzzword in healthy eating—it plays a big role in everything from gut health to weight management. But have you ever wondered why some people react differently to high-fiber foods? The truth is, not all fiber is created equal.

What is Fiber and How Is It Classified?

In simple terms, fiber is a group of carbohydrates that our bodies can’t digest because we lack the necessary enzymes. Instead of being broken down, fiber passes through our digestive tract mostly intact. Experts suggest men should aim for about 38 grams daily and women about 25 grams, yet most people only consume around 15–17 grams. Most of this fiber comes from plant foods like vegetables, fruits, legumes, whole grains, nuts, and seeds.

Fiber is traditionally divided into two types:

• Dietary fiber: Naturally occurring in your whole foods.
• Functional fiber: Extracted from food sources and added to processed items.

However, this classification doesn’t really explain how different types of fiber affect your health.

Soluble vs. Insoluble Fiber

Fiber is often sorted into soluble and insoluble types based on its ability to dissolve in water:

• Soluble fiber: Mixes with water to form a gel-like substance. This can help reduce blood sugar spikes and improve metabolic health.
• Insoluble fiber: Doesn’t dissolve in water and works as a natural bulking agent to move food and waste through the digestive system.

Different plants offer varying amounts of each type, meaning each fiber source can provide unique health benefits.

Fermentable Fiber

Did you know that your colon is home to about 100 trillion bacteria? These helpful microbes, sometimes called the “forgotten organ,” play a key role in value-added processes like weight management and immunity. Fermentable fiber is the kind that these bacteria break down for energy, producing short-chain fatty acids that offer powerful health benefits. Just a heads-up: if you’re not used to eating a lot of fiber, you might experience some gas or bloating—that’s a normal byproduct of the fermentation process.

Viscous Fiber

Some soluble fibers are special because they form a thick, gel-like consistency when mixed with water. Known as viscous fibers, they slow digestion and the absorption of nutrients, which keeps you feeling full for longer. This can help naturally reduce your appetite and may even aid in weight loss. Foods such as legumes, oats, and flax seeds are excellent sources of this fiber.

Resistant Starch

In our everyday diet, starch is a major carbohydrate found in foods like potatoes and grains. However, a portion of this starch is resistant to digestion and passes through our system, similar to soluble, fermentable fiber. Resistant starch offers many of the same benefits, such as enhancing digestive health, improving insulin sensitivity, and lowering blood sugar levels. You can find it in green bananas, legumes, and even in cooled white potatoes or rice.

Unique Fibers Worth Highlighting

There are some unique fibers that deserve a closer look:

• Fructans: These are small chains of fructose molecules that nourish gut bacteria and may help with some types of diarrhea. However, they’re part of the FODMAP family, which can cause digestive discomfort, particularly in individuals with IBS.
• Beta-Glucans: Found in oats and barley, these fibers are very viscous and can help lower cholesterol, improve insulin sensitivity, and extend feelings of fullness.
• Glucomannan: Often used as a weight loss supplement, this viscous fiber has shown promise in reducing appetite, fighting constipation, and even improving heart health markers.

Take Home Message

In a nutshell, the best kinds of fiber are the soluble, viscous, and fermentable types—plus, resistant starches add great value too. Instead of worrying over every detail, aim to fill your plate with a rainbow of whole plant foods like vegetables, fruits, oats, legumes, nuts, dark chocolate, avocado, and chia seeds. When you do, you'll naturally get a mix of fibers to keep your digestive system—and overall health—in top shape.