Is it bad if I don't eat enough fiber? Understanding the Risks

January 2, 2026 •

2 min read

Over 90% of American adults fail to meet their recommended daily fiber intake, often averaging only half the suggested amount. This common dietary shortfall begs the question: is it bad if I don't eat enough fiber, and what are the specific health consequences for your body?

Quick Summary

Not consuming adequate fiber is detrimental to your overall health, causing immediate digestive distress, unstable energy levels, and increasing your long-term risk for various chronic diseases.

Key Points

Constipation & Hemorrhoids: A low-fiber diet is a primary cause of constipation, which can lead to painful hemorrhoids due to straining.
Increased Disease Risk: Insufficient fiber is linked to a higher risk of heart disease, type 2 diabetes, and certain cancers, particularly colorectal cancer.
Weight Management Challenges: Without fiber's filling effect, you may feel hungry sooner and be more prone to overeating and unwanted weight gain.
Gut Health Disruption: A lack of fiber starves beneficial gut bacteria, leading to an unbalanced gut microbiome and related inflammatory and digestive issues.
Fluctuating Energy Levels: Insufficient fiber causes blood sugar spikes and crashes, which can lead to fatigue, tiredness, and mood swings.
High Cholesterol: Low soluble fiber intake allows excess cholesterol to be reabsorbed into the body rather than being excreted.
Poor Skin Health: A compromised gut-skin axis resulting from low fiber intake can manifest as dull, dry, or inflamed skin.

The Immediate Impact: Digestive Distress

A low-fiber diet primarily impacts the digestive system. Insoluble fiber adds bulk to stool, aiding its movement through the intestines. Insufficient fiber slows this process, leading to uncomfortable issues.

Symptoms of Poor Digestion

Constipation: A common symptom of low fiber, resulting in hard, dry, and difficult-to-pass stool.
Hemorrhoids and Anal Fissures: Straining from chronic constipation can pressure rectal veins, causing hemorrhoids or anal fissures.
Bloating and Stomach Pain: Slow digestion can cause waste buildup, leading to bloating and discomfort.

Long-Term Consequences of a Low-Fiber Diet

Beyond immediate discomfort, a lack of fiber increases the risk of several serious long-term conditions.

Increased Risk of Chronic Diseases

Heart Disease: Soluble fiber helps lower LDL cholesterol. Low intake contributes to higher cholesterol and heart disease risk.
Type 2 Diabetes: Fiber moderates sugar absorption, stabilizing blood sugar. Low fiber leads to rapid sugar spikes, increasing type 2 diabetes risk over time.
Weight Gain: High-fiber foods are filling and help control appetite. A low-fiber diet can lead to overeating and weight gain.
Diverticular Disease and Colorectal Cancer: Insufficient fiber may weaken intestinal walls, potentially forming diverticula that can become inflamed (diverticulitis). A link also exists between low fiber and increased colorectal cancer risk.
Gut Microbiome Imbalance: Beneficial gut bacteria rely on fiber. Low fiber can cause dysbiosis, leading to inflammation and digestive issues.

Soluble vs. Insoluble Fiber: A Comparative Look

Both soluble and insoluble fiber are essential for health.


Characteristic	Soluble Fiber	Insoluble Fiber
Source	Oats, peas, beans, apples, carrots, citrus fruits, barley	Whole-wheat flour, wheat bran, nuts, green beans, potatoes (with skin)
Function	Forms a gel, slowing digestion.	Adds bulk to stool.
Effect on Stool	Softens stool by absorbing water.	Adds mass and speeds transit.

Increasing Your Fiber Intake: Simple Steps

Boosting fiber intake is simple and beneficial. Easy ways to increase fiber include:

Choosing whole grains over refined options.
Adding legumes to meals.
Snacking on fruits, vegetables, nuts, and seeds.
Eating potatoes with their skins.
Increasing intake gradually and drinking plenty of water.

Conclusion: Prioritizing Fiber for Long-Term Health

Not eating enough fiber is detrimental to health, causing immediate digestive problems and increasing the risk of chronic diseases like heart disease, type 2 diabetes, and certain cancers. Fiber is crucial for overall wellness, supporting digestion, blood sugar, cholesterol, and gut health. Incorporating more fiber-rich whole foods can improve digestive health, aid weight management, and reduce chronic disease risk. For more information on high-fiber foods, consult resources like the National Cancer Institute's guide.

Frequently Asked Questions

Common signs include constipation, irregular bowel movements, bloating, fatigue, feelings of hunger soon after eating, blood sugar fluctuations, and weight gain.

The recommended daily intake for adults is typically 25 grams for women and 38 grams for men, though many people fall short of this amount.

While uncommon with food-based sources, consuming excessive amounts of fiber, particularly from supplements without enough fluid, can cause abdominal pain, gas, and bloating. A sudden increase can also cause discomfort.

Good sources of soluble fiber include oats, beans, lentils, peas, apples, citrus fruits, carrots, and barley.

Foods rich in insoluble fiber include whole-wheat flour, wheat bran, nuts, seeds, the skins of fruits and vegetables, and green beans.

Fiber supplements can help, but it's generally best to get fiber from whole foods, which also provide essential vitamins and minerals. If using supplements, increase water intake to prevent constipation.

It's best to increase your fiber intake gradually to allow your digestive system time to adjust. A sudden increase can cause gas and bloating.

Yes, low fiber intake can lead to unstable blood sugar levels, causing mood swings and fatigue. A balanced gut microbiome, which is supported by fiber, is also linked to better mental well-being.