The importance and benefits of fiber in your diet

Table of contents:

What's dietary fiber?

Fiber for weight loss

Fiber and performance

Fiber recommendations

Some final words on fiber

Are you getting enough fiber?

Although fiber isn’t considered an essential nutrient, consuming fiber is an essential part of a healthy diet. Fiber supports both gut and cardiometabolic health, warding off a variety of diseases from type 2 diabetes(1) to colorectal cancer(2).

And the benefits of fiber aren’t just limited to overall health: eating a high-fiber diet can help you achieve your fitness goals by curbing hunger throughout a weight loss phase(3).

So if you haven’t considered your fiber intake, it’s time to start.

Let’s take a deep dive on dietary fiber. By the end of this article, you’ll understand what fiber is, why you should consume it, how much you should get daily, and how to track it.

What’s dietary fiber?

Dietary fiber is a type of carbohydrate that digestive enzymes in the small intestine are unable to break down. However, some forms of fiber can be digested and fermented by bacteria found in the large intestine.

Fibers can be categorized based on their solubility, viscosity, and fermentability. The most common distinction used is soluble/insoluble fiber - both of which are present in plants and confer a number of health benefits(4).

Soluble Fiber

Soluble fiber refers to fiber that can dissolve in water. Most soluble fibers are viscous and fermentable. That is, they form a thick gel in water and are broken down by bacteria in the large intestine.

The gelatinous substance created with soluble fiber slows gastric emptying, which helps support satiety and stabilize blood sugar levels by slowing the rate at which carbs are absorbed into the bloodstream.

Additionally, many soluble fibers are considered prebiotics, as they feed large intestinal bacteria to promote a healthy gut microbiome. Fermentation of soluble fiber also creates short-chain fatty acids, which have several positive effects on health(5), such as…

  • Lowering cholesterol and triglycerides(6, 7)
  • Lowering inflammation(8)
  • Reducing risk of cardiovascular disease(9)
  • Preventing cancer (specifically colon cancer)(10)
  • Preventing type 2 diabetes(11)

Good sources of soluble fiber include…

  • Beans and legumes
  • Fruits
  • Oats
  • Nuts and seeds
  • Vegetables

Insoluble Fiber

Insoluble fiber does not dissolve in water and is typically nonfermentable, such that it passes through the entire gastrointestinal tract intact. Insoluble fiber is most recognized for regulating gut motility by increasing the bulk of stool, which can help alleviate constipation(12).

Nonetheless, insoluble fiber is also beneficial for…

  • Regulating blood sugar levels and preventing type 2 diabetes(13)
  • Increasing satiety(14)
  • Preventing colorectal cancer(10)
  • Reducing risk of hemorrhoids and diverticulitis (small pouches in your colon)(15, 16)

You can find insoluble fiber in foods like…

  • Fruits (especially the skins)
  • Nuts and seeds
  • Vegetables (especially the skins)
  • Whole grains

Fiber for weight loss

It’s well-established that consuming dietary fiber can help support weight loss. For instance, a recent meta-analysis found that participants supplementing with soluble fiber lost as much as 5.5 pounds(19)!

There are several means by which fiber intake influences weight loss(20), such as…

Supporting dietary adherence by supporting satiety and keeping you fuller longer

Fiber enhances satiety signals by slowing down digestion and expanding in the digestive tract. Additionally, fibrous foods often take longer to eat, which allots sufficient time for satiety signals to reach your brain before you grab a second serving.

Allowing you to eat more at lower calories

Fibrous foods tend to be less energy dense, so you can eat a higher volume of food without overconsuming calories. Moreover, since some fibers aren’t completely digested, they contribute less to your total calorie intake than non-fibrous carbs.

Staving off hunger by stabilizing blood sugar

Because fiber slows the rate at which carbs are absorbed into the bloodstream, it helps regulate blood sugar levels. And as a result, you can sidestep the hunger and cravings that often accompany large spikes and dips in blood sugar.

Reducing absorption of macronutrients

Fiber can reduce absorption of other macronutrients (i.e. protein and fats) - so you likely absorb fewer calories on a high-fiber diet, which can help you more easily create a calorie deficit.

What’s more, eating enough fiber during a weight loss phase is crucial for digestive health - and without proper planning, cutting calories can concomitantly cut fiber.

Luckily, a few simple swaps can help keep your fiber intake (and diet) on track. Specifically, you can…

  • Consume whole grains instead of refined grains (i.e. brown over white rice).
  • Eat plenty of vegetables.
  • Focus on whole fruits, including the skin.
  • Find lower-calorie snacks that are high in fiber, such as popcorn or puffed quinoa.
  • Use beans and legumes as a carb source for your meals.⁠
  • Let your cooked starches (i.e. potatoes, rice, pasta) cool before eating them.

Despite the apparent weight loss benefits of fiber, you may notice an unexpected jump in weight upon increasing your fiber intake. Such weight fluctuation is normal and typically reflects increased water retention or digestive content (i.e. more mass moving through your gut), not fat gain. Your weight will stabilize once you stabilize your fiber intake.

Fiber and performance

It’s important to realize that more fiber isn’t always better - especially when it comes to exercise performance.

To optimize workouts, you should eat sufficient carbs in your pre-workout meal to properly fuel performance. For some, eating high-fiber carbs shortly before your workout can cause GI distress and hurt more than help. If you have had GI distress before it might be good to opt for lower-fiber carbs to ensure that you digest and absorb them quickly enough to use during your workout - and to avoid unnecessary gut issues.

Fiber recommendations

To reap the many benefits of fiber, you’ll want to hit the sweet spot for fiber intake - neither too little nor too much, as either extreme can hinder gut health.

For example, both excessively high- and low-fiber diets can cause…

  • Bloating
  • Constipation
  • Gas
  • Abdominal discomfort

The current USDA guidelines recommend 14 grams of fiber for every 1000 calories consumed, which works out to ~25-30 grams daily on a ~2000 calorie diet and ~35-40 grams daily on a ~2500 calorie diet.

Nonetheless, these are general recommendations, which are a good starting point but neglect individual differences. Accordingly, you can start with the recommended intake and adjust slightly upward or downward depending on your digestion and gastrointestinal comfort.

If you decide to increase your fiber consumption, be sure to do so gradually, to thoroughly chew your food, and to drink sufficient water.

How to track fiber

It’s often mistakenly assumed that fiber has zero calories. In truth, fiber contains approximately ~2 calories per gram. Soluble fiber, in particular, is better digested than insoluble fiber and thus contributes more calories toward your total daily calorie intake.

So, although fiber contains nearly half the calories as other carbs, you should still count it when tracking your macros.

Some final words on fiber

What happens in the gut doesn’t stay in the gut.

While dietary fiber is often associated with digestive health, its benefits extend far beyond the bowels.

Whether you want to ward off diabetes, promote longevity, or lose a little weight, eating enough fiber can help you achieve your goal.

But that isn’t to say that fiber is a cure-all, and it’s certainly not some calorie-free miracle nutrient.

Fiber is a fundamental feature of a healthy diet - but it isn’t the sole feature of a healthy diet. And it must be considered in the context of the entire diet.

Using a fiber supplement as a band-aid for a diet full of ultra-processed, micronutrient-poor foods will only get you so far. In the end, eating a diet full of fiber-rich whole foods will work more magic than any quick fix or supplement.

So prioritize fiber in addition to an overall nutritious diet. Your gut, heart, body, and mind will thank you.

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  1. Aune, D., Chan, D. S., Lau, R., Vieira, R., Greenwood, D. C., Kampman, E., & Norat, T. (2011). Dietary fibre, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies. Bmj, 343.
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  1. Prasad, K. N., & Bondy, S. C. (2019). Dietary fibers and their fermented short-chain fatty acids in prevention of human diseases. Bioactive carbohydrates and dietary fibre, 17, 10017
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  1. Arayici, M. E., Mert-Ozupek, N., Yalcin, F., Basbinar, Y., & Ellidokuz, H. (2022). Soluble and insoluble dietary fiber consumption and colorectal cancer risk: a systematic review and meta-analysis. Nutrition and Cancer, 74(7), 2412-2425.
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