The hidden dangers of a low-fiber diet, according to nutritionists

Fiber isn’t just a wellness trend, it’s an essential nutrient for digestion, steady energy, and long-term health. 

Yet many adults fall short of the recommended daily intake, which experts say can lead to a host of health problems.

Registered dietitians say the average adult should aim for 25 to 38 grams of fiber per day, but only around 7% of Americans meet that target.

Common reasons for the deficit include low consumption of fruits, vegetables, legumes, and whole grains, and a preference for refined snacks and processed foods.

Digestive issues

Fiber comes in two forms: soluble and insoluble. Soluble fiber, found in oats, beans, and apples, absorbs water to soften stool, while insoluble fiber in whole grains, nuts, and vegetables adds bulk and speeds waste through the gut. Without enough fiber, stools become harder, slower to pass, and constipation can develop within just a few days.

Reduced fullness and weight challenges

Fiber-rich foods increase satiety by slowing digestion and promoting fullness signals to the brain. Low-fiber diets can leave you hungry soon after meals, leading to overeating and difficulty managing weight.

Heart and Blood Sugar Concerns

Soluble fiber helps lower LDL cholesterol and stabilizes blood sugar. Insufficient fiber may contribute to high cholesterol, insulin resistance, and a higher risk of diabetes.

Increased cancer risk

Low fiber intake has been linked to colorectal cancer. Fiber helps move waste through the digestive tract and feeds beneficial gut bacteria, which produce compounds that protect colon cells.

Signs you need more fiber

Experts suggest you may need more fiber if you experience fewer than three bowel movements per week, hard stools, bloating, frequent hunger, or energy dips between meals.

Tips to boost fiber intake

Gradually add fiber-rich foods like fruits, vegetables, legumes, nuts, and whole grains. Increase your intake slowly to prevent gas and bloating, and drink plenty of water to support smooth digestion.

“Think of fiber like training a muscle — your gut needs time to adjust,” says Laurie Allen, RDN. A measured approach ensures comfortable digestion while reaping the full health benefits.