Constipation and Fiber: Why Adding More Makes Things Worse
For decades, we’ve been told the same story: if you’re constipated, add more fiber. It’s a message echoed by doctors, dietitians, and the glossy labels on cereal boxes. The logic seems simple. Fiber bulks up stool, which should make it easier to pass. But when you start digging into the science, the story unravels. Far from being a cure, fiber may actually be the reason so many people are constipated in the first place.
In 2012, a team of researchers led by Dr. Kamal Ho published a clinical study that should have changed the conversation forever. The trial followed patients with chronic constipation who were divided into three groups. One group kept eating high-fiber diets, another reduced their fiber, and a third eliminated it completely. The results were remarkable. Those who stopped eating fiber entirely went from one bowel movement every 3.75 days to one every single day, and their bloating and straining disappeared. Those who reduced fiber also saw improvements, averaging a bowel movement every 1.9 days. But the patients who stayed on high-fiber diets saw no change at all, still struggling to go once every seven days. In other words, less fiber led to more regularity, not less.
The body’s physiology helps explain why. Fiber is indigestible, so it doesn’t nourish us, it simply adds bulk. That bulk holds water and stretches the bowel wall, requiring stronger contractions to move things along. Instead of speeding up the process, fiber often slows transit time, especially in people who already have motility issues. To make matters worse, fermentable fibers feed gut bacteria and release gas, which can cause bloating and discomfort. And because fiber binds to nutrients and moves food more quickly through the gut, it can also prevent the absorption of vitamins and minerals. What is promoted as a digestive aid is, for many, a digestive burden.
Nutrition researcher Dr. Zoë Harcombe has spent years questioning the unquestionable, and fiber is one of her favorite targets. She reminds us of something often overlooked:
“There are essential fats, there are essential proteins, there are no essential carbohydrates. Fibre is a subset of carbohydrate. De facto, there is no requirement for fibre whatsoever.”
That one statement changes everything. If fiber is not required, why are we told it’s indispensable? The answer is rooted less in science and more in history. In the 1800s, reformers such as Sylvester Graham and John Harvey Kellogg, both Seventh-day Adventists, believed that meat fueled sin and immorality. They promoted whole grains and plant-based foods as virtuous alternatives, laying the foundation for an early vegetarian movement. Their influence carried forward into the 20th century, when cereal companies adopted their ideas, not as a mission but as a business model. Fiber became a convenient selling point for grains, even as products like bran flakes were loaded with sugar to disguise their taste.
The health halo of fiber was never built on robust evidence. It was born out of religious ideology, then amplified by marketing campaigns that turned “whole grains” into a symbol of virtue. If you’d like to explore this background more deeply, I’ve written about it here: The Dark Origins of Veganism: How a Religious Agenda Hijacked Nutrition and Health
The cycle doesn’t end there. People who suffer constipation are told to eat more fiber, often worsening their symptoms. When that fails, they’re prescribed laxatives, stool softeners, or more powerful medications. The root cause fiber itself is never addressed. This keeps patients dependent on both “healthy whole grains” and pharmaceuticals, neither of which resolve the problem.
My own experience echoes the science. After ten years on a keto lifestyle, I transitioned to an animal-based diet. I never once dealt with constipation. The reason is simple: animal foods are so nutrient dense and bioavailable that the body absorbs nearly everything. Very little is left behind. Digestion feels efficient and complete. Contrast that with a high-fiber vegetarian diet where nutrients are harder to access, and supplementation becomes necessary. Fiber doesn’t just fail to help; it actively prevents the body from getting what it needs.
Yet despite the evidence, you won’t hear about studies like Ho’s in mainstream headlines. Why would you, when admitting the truth would undermine decades of dietary guidelines, food marketing campaigns, and pharmaceutical profits? It’s more convenient to keep repeating the mantra that fiber cures constipation, even when clinical evidence shows the opposite.
The lesson here is not only about digestion, but about how we approach nutrition in general. We’ve been told the same story for decades without being encouraged to question it. But science moves forward by asking uncomfortable questions, by revisiting assumptions, and by turning popular narratives upside down when the evidence demands it. Constipation is not a fiber deficiency. It’s a signal that something else is off, and for many people the solution is not more bulk but less.
As Harcombe bluntly puts it:
“If we don’t need it, is it good for us? And the short answer is no.”
Fiber has been marketed as indispensable, but the science shows otherwise. If you’ve ever increased fiber only to feel more bloated, more uncomfortable, and more dependent on medication, you’re not imagining it. The truth is that our bodies know what to do without it. What they need is real, nutrient-dense food that fuels us fully and leaves little behind. That’s not a problem. That’s the way digestion is meant to work.
References
Ho, K. S., Tan, C. Y., Mohd Daud, M. A., Seow-Choen, F., & Goh, H. S. (2012). Stoppage of dietary fiber intake reduces constipation and its associated symptoms. World Journal of Gastroenterology, 18(33), 4593–4596. PubMed PMID: 22969234
Harcombe, Z. (2022). Fibre – ask why, not how. Retrieved from zoeharcombe.com
Harcombe, Z. (2025). 12 Questions about Fibre. Retrieved from zoeharcombe.com
Defeat Diabetes (2023). The Fibre Myth with Zoë Harcombe. Retrieved from defeatdiabetes.com.au
This content is never meant to serve as medical advice.
In crafting this blog post, I aimed to encapsulate the essence of research findings while presenting the information in a reader-friendly format that promotes critical thinking and informed decision-making.
