Key Takeaways
Getting enough fiber is essential for healthy digestion, steady energy, and reducing the risk of long-term health issues.Without enough fiber, you may experience constipation, hunger soon after meals, and even increased risks of heart disease or diabetes.To boost fiber intake, gradually add fiber-rich foods like fruits, vegetables, and whole grains, and drink plenty of water.
Recently, fiber has been a hot topic in the wellness space—but it’s not just another trend. The nutrient is essential for optimal digestion and overall health. And yet, many of us aren’t getting enough, which can lead to both short-term and long-term health issues. Not convinced? We spoke to registered dietitians to learn what happens to your body when you don’t get enough fiber. They also explain how to know if you’re getting enough.
How Much Fiber Do You Need?
“The average adult needs between 25 and 38 grams of fiber per day,” says Roxana Ehsani, MS, RD, CSSD, LDN, sports dietitian and adjunct instructor at Virginia Tech. However, only about 7 percent of the population currently meets daily fiber requirements, she notes.
There are several reasons why so many of us aren’t getting enough fiber. For starters, most folks don’t consume enough fiber-rich foods, such as fruits, vegetables, and legumes like beans or peas, according to Ehsani. People also tend to choose refined over whole grains, she says. Additionally, common snacks (such as chips and soda) are low in fiber, further widening the fiber gap.
What Happens If You Don’t Eat Enough Fiber
Without enough fiber, here’s what will happen to your body.
Constipation and Digestion Issues
There are two types of fiber, soluble and insoluble, and both play important roles in regular bowel movements, says Laurie Allen, RDN, LDN, professor of nutrition and director of didactic program in dietetics nutrition at UNC Greensboro. “Soluble fiber, found in foods like oats, beans, and apples, dissolves in water to form a gel that softens stool and makes it easier to pass,” Allen says. “Insoluble fiber, found in whole grains, nuts, and vegetables, adds bulk to stool and speeds up the movement of waste through the digestive tract,” notes Allen.
Thus, without enough fiber in your diet, you’re bound to experience gastrointestinal issues like constipation. It can also occur quickly, within 1 to 3 days of reduced fiber intake, Allen says. “When fiber intake drops, stool becomes smaller in volume and moves more slowly through the colon,” says Allen. As it lingers here, it loses water, becoming firm and increasingly difficult to pass, she notes.
Reduced Satiety
“High-fiber foods add volume to meals, slow gastric emptying, and stimulate hormones that signal fullness to the brain,” says Allen. Plus, many fiber-rich foods require more chewing, which naturally slows eating and allows time for fullness signals to register, Allen says. So, “when meals are low in fiber, you may feel hungry sooner, which may lead to overeating or snacking,” says Ehsani. This can make weight management challenging and negatively impact overall health, notes Ehsani.
Poorly Managed Cholesterol
“Over time, consuming a high-fiber diet can support healthy cholesterol levels,” says Ehsani. That’s because soluble fiber helps lower LDL (“bad”) cholesterol by binding to cholesterol in the digestive tract and removing it from the body, she says. In contrast, eating a low-fiber diet may contribute to consistently elevated cholesterol levels, potentially increasing the risk of heart disease, says Ehsani.
Unstable Blood Sugar Levels
Fiber slows the digestion and absorption of carbohydrates, which helps keep your blood sugar levels steady, says Ehsani. So, without enough fiber, your blood sugar might rise and fall more quickly after meals, she notes. Eventually, this can contribute to unstable blood sugar levels, potentially leading to blood sugar issues like insulin resistance or diabetes, says Ehsani.
Higher Risk of Some Cancers
“Chronically low fiber intake has been associated with an increased risk of certain cancers, particularly colorectal cancer,” says Allen. Here’s why: “Insoluble fiber helps move waste through the digestive tract more quickly, reducing the amount of time potentially harmful substances remain in contact with the colon lining,” Allen says. Meanwhile, soluble fiber acts as a prebiotic, feeding beneficial gut bacteria that produce protective compounds that help reduce inflammation and support healthy colon cells, she notes. However, consistently low fiber intake can reduce these protective effects, leading to a higher risk of colorectal cancer, says Allen.
How to Know You’re Getting Enough Fiber
If you’re meeting your fiber needs, you may notice the following signs, according to Allen:
Predictable and comfortable digestionRegular bowel movements that are easy to pass without strainingStools that are soft and well-formedPredictable, comfortable digestion with minimal bloatingFeeling satisfied after mealsFewer cravings between mealsSteadier energy levels throughout the day
Signs of low fiber intake might show up as:
Fewer than three bowel movements per weekHard, dry, or difficult-to-pass stoolsBloating or discomfortStraining or a lingering feeling of not being “fully” finished after a bowel movementFrequent hunger soon after eatingEnergy dips or cravings between meals
How to Increase Your Fiber Intake
If you’re one of the many people who need more fiber, it can be tempting to quickly increase your intake. However, you’ll want to do it slowly. “Think of it like training a muscle. Your gut needs a ‘warm up’ period to handle more bulk,” says Allen. “Large, sudden increases in fiber are more likely to cause gas, bloating, and abdominal cramps, so it’s best to increase intake gradually to give your digestive system time to adjust,” she says.
Allen offers a practical tip: “Add a few grams of fiber each day or introduce one fiber-rich food at a single daily meal until you reach your goal.” It’s also important to drink more water as you increase your fiber intake. Adequate hydration will help keep stool soft and support comfortable digestion, says Allen.