A women eating a bowel or cereal trying to increase fiber

How Much Fiber Should You Have Daily? 6 Myths Debunked

If you are new to the keto diet, you probably have some concerns about whether or not the recommended foods will provide you with enough fiber. The truth is that lowering and almost eliminating fiber in your diet will have huge benefits.

This article will examine the myths surrounding the so-called benefits of fiber and highlight some research that debunks these myths. 

Credit for most of the information provided in this post and the associated research links goes to Dr. Ken Berry. Whether you are looking to start keto or have been following keto for years, Dr. Berry is a fantastic resource to help you cut through the BS.

What is Fiber?

Fiber is simply plant material that we cannot digest. It is categorized in two ways, soluble fiber, which dissolves in water, and insoluble fiber, which does not.

Google the word fiber, and you will be inundated with dozens of unsubstantiated benefits of fiber, including; lowering blood pressure, blood sugar, and cholesterol, improving bowel movements, preventing colon cancer, promoting weight loss, and helping detoxify the body. 

Despite all of the hype, it might surprise you that there is little to no legitimate scientific support for these claims about fiber.

We Didn’t Need Fiber Before, So What Changed?

As a biologist, I have studied animals’ and humans’ diets and digestive physiology. Evolutionarily and biologically, humans are categorized as facultative carnivores. A facultative carnivore is primarily a meat-eater that cannot thrive without animal-based foods. 

What makes a carnivore facultative is its ability to subsist, for a time, on some types of plant material; however, this is a survival mechanism and not optimal long term.

Why not? We simply aren’t designed to digest plant cellulose and therefore cannot secure adequate nutrition from an all-plant diet without supplementation. Mammalian herbivores are equipped with specialized stomachs, sometimes multiple and long, complex digestive tracts, to facilitate microbial fermentation. 

On the other hand, humans have a single acid-based stomach and relatively short and simple intestines or guts, just like other carnivores. During millions of years of evolution, the diets of humans consisted of predominately meat and a variety of tart fruits, nuts, and seeds when seasonally available.

Where it all Went Wrong

Many people attribute the push towards high fiber diets to Dr. Denis Parsons Burkitt, also known as The Fiber Man

In his 1979 book Don’t Forget Fiber In Your Diet, Dr. Burkitt concluded that many western diseases, which were rare in Africa, resulted from diet and lifestyle and were associated mainly with low fiber intake.

While he did identify other dietary differences between Africans and Westerners, such as the near absence of processed foods, and the higher consumption of animal fats, he mistakenly credited higher fiber intake for the health benefits.

He also had an alternative theory that using the natural squatting position during defecation protected natives of Africa and Asia from gastrointestinal diseases. It’s a good thing this was a secondary theory; otherwise, he may have ended up with a much different nickname.

Dr. Burkitt was a very respected surgeon and made other significant contributions to medical science, including the identification, distribution, and etiology of what is now known as Burkitt’s Lymphoma, so his theories surrounding fiber were essentially accepted gospel. 

It is important to note that the theories he presented in his book had not been tested and were essentially an educated guess or hunch based on how he interpreted his observations. 

Myth #1 – Fiber Supports Healthy Weight Loss

While there is evidence that fiber can contribute to weight loss, the manner in which it works is not exactly healthy.

The approach is simple. We can’t digest fiber, so it sits in our digestive tract for long periods making us feel full. Because we feel full, we eat less, and by eating less, we ultimately lose weight. 

It seems like a logical approach, but here’s the problem. Fiber provides no nutritional value, and therefore consuming large amounts results in less room for more nutritious foods. 

Holding a bulk of fiber in our systems also interferes with the proper digestion of other foods consumed along with the fiber. Many recommended high-fiber foods, such as wheat and other grains, actually trigger hunger and impede the absorption of nutrients.

Want a better way to curb hunger and lose weight? Eat more protein and fat.

Myth #2 – Fiber Helps Relieve Constipation

Adding fiber, when constipated, further slows digestion and, in the case of soluble fiber, absorbs moisture, making things worse. It is the equivalent of adding toilette paper to help unblock a toilette.

Eating less fiber and staying well hydrated are the best ways to prevent constipation, and consuming a few tablespoons of apple cider vinegar diluted in water is a great way to get things moving. 

Research Link – Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms.

Myth #3 – Our Healthy Bacteria Need Lots of Fiber

While it is true that our gut bacteria can break down small amounts of fiber, this doesn’t mean that consuming fiber provides any real benefit. 

Remember, there is no nutrition in fiber so breaking it down is of little benefit to us or the bacteria. What is produced from breaking it down is a small amount of short-chain fatty acids, which are better sourced elsewhere, and loads of gas.

That’s right. The bloating, cramping, and gas you have been experiencing while loading up on fiber is due to the methane and carbon dioxide released when your gut bacteria attempt to break down fiber.

One of the most immediate and profound changes many people notice when going keto or carnivore is no more bloating or gas. 

Myth #4 – Fiber Lowers Blood Sugar & Cholesterol

Like the weight loss myth, there is some support for fiber in lowering blood sugar and cholesterol, but increasing fiber intake is not the best way to address these issues.

If 10-15% of your diet is fiber, you are technically eating less actual food, and therefore your blood sugar and cholesterol may go down; however, there are far better ways to accomplish this.

First off, consuming fewer carbohydrates and sugar will have a far more significant influence on lowering blood sugar and insulin. Second, cholesterol is not the problem when it comes to heart disease; inflammation is.

Myth #5 – Fiber Helps Prevent Colon Cancer

Proponents of high fiber diets will almost always claim that large amounts of fiber are beneficial for ‘scrubbing’ the interior walls of the colon, thus improving the health of the colon and preventing colon cancer.

As mentioned above, maintaining a bulk of indigestible fiber in our guts interferes with the proper digestion of food and the absorption of nutrients. 

It is also unnecessary to run a Brillo pad of fiber through your colon, and doing so can damage the walls of the colon.

The next time someone argues that high fiber diets help prevent colon cancer, present them with the following studies.

The first study, linked here, is a meta-analysis of five randomized controlled trials in humans, which is important to note. The reviewers hypothesized that eating more fiber would decrease the risk of colon cancer.

Their conclusion, however, was – There is currently no evidence from randomized controlled trials to suggest that increased dietary fiber will reduce the incidence or recurrence of adenomatous polyps (the precursors of colon cancer) within a two to four year period.

The second study, linked here, is a meta-analysis of 13 cohort studies from pooled data involving 725,628 men and women over a 6-20 year period. 

The conclusions of this study – In this extensive pooled analysis, dietary fiber intake was inversely associated with the risk of colorectal cancer in age-adjusted analysis. However, after accounting for other dietary risk factors, high dietary fiber intake was not associated with a reduced risk of colorectal cancer.

Myth #6 – Fiber Supports Detoxification

Google “how to detox your body?” You will be hit with a barrage of people promoting products that they claim will help remove toxins from your body, most of which are just overpriced and unnecessary fiber supplements.

The best way to detoxify your body is to fast, period.


Before the agricultural revolution, humans thrived by consuming predominately fatty meats and little to no fiber, and our physiology has not changed.

Most of the past literature promoting the consumption of high fiber foods has been debunked by more current and robust research, and we are learning more and more each day just how far we have gone off course in our diets due to the influence of the food industry.

Have you tried reducing fiber in your diet? How did you feel? Please consider sharing your experience by commenting below to help others live a fit keto lifestyle.

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