Odds are, you’re not eating enough fiber. A carbohydrate found in plant-based foods, it plays a significant role in bodily functions: It makes you feel full and keeps your digestive system moving. It also helps regulate blood sugar, blood pressure, and cholesterol levels, so it’s especially valuable for people with type of diabetes or heart disease. There are certain signs your body needs more fiber (that go beyond constipation).

“Fiber is your body’s built-in cleanup crew,” says Samantha Peterson, R.D., founder and CEO of Simply Wellness. “It’s not flashy, but it’s powerful.”

You need between 21 and 38 grams per day (depending on your age and gender)—and most Americans consume half that, per Statpearls. Experts blame this on our diets being low in fiber-rich fruits and vegetables, and high in fiber-poor processed foods. But they say lack of awareness may also play a role. “People may not realize how much fiber they need,” says Erin Barrett, Ph.D,, director of product innovation and scientific affairs at Shaklee. “Without that understanding, it’s easy to fall short.”

Meet the experts: Samantha Peterson, R.D., founder and CEO of Simply Wellness; Erin Barrett, Ph.D., director of product innovation and scientific affairs at Shaklee; Amy Davis, R.D.N., Live Conscious nutrition consultant; Matt Landry, Ph.D., R.D.N., assistant professor at UC Irvine Joe C. Wen School of Population & Public Health.

Running low on fiber can cause uncomfortable symptoms, like gas, bloating, and constipation. And since fiber does more than regulate your digestive system, it may impact your skin, mood, and immune system too.

Ahead, experts explain signs and symptoms associated with needing more fiber in your diet.

Signs you’re not getting enough fiberConstipation

The experts we spoke to agree: Constipation is a classic sign you need more fiber. “Without enough fiber, waste moves slowly through our intestines, becoming hard and difficult to pass,” Landry explains. If you’ve gone a few days without spending time on the toilet, low fiber may be to blame, Peterson says.

Irregular poops

Irregular poops—poops that are infrequent, uncomfortable, or unusual-looking—are another telltale sign you’re low on fiber. “Fiber bulks up the stool and helps move things along,” Davis explains. Without enough fiber, your poops may be small, hard, and pebble-like, rather than healthy, smooth, and continuous.

Constant cravings

If you’re constantly craving snacks—or feeling hungry right after you’ve eaten—you may need more fiber in your diet. “Fiber helps increase satiety by slowing digestion and promoting a feeling of fullness,” Barrett explains. “Without it, meals may not feel as satisfying.” Not getting enough fiber may also lead to a blood sugar spike or crash, Peterson notes, which may cause you to crave sweets and other foods, per the American Diabetes Association (ADA).

Mood swings

Suddenly feeling grumpy or struggling to focus? Peterson and Davis say these could be signs you’re low on fiber. “Not getting enough fiber can impact your mood,” Davis says. That’s because fiber helps regulate your gut, Peterson explains. And your gut produces important neurotransmitters, like mood-regulating serotonin, feel-good dopamine, calming GABA (gamma-aminobutyric acid), and brain-friendly glutamate.

Bloating

When you don’t get enough fiber, it can throw off your entire digestive tract—causing symptoms like gas, bloating, and general discomfort. “Fiber helps regulate digestion, feed your gut bacteria, and stabilize blood sugar,” Peterson says. “Without it, your whole system can feel off.” Low fiber can disrupt the delicate balance of bacteria in your gut, Barrett adds, causing your digestive system to go haywire.

Dull skin

One lesser-known symptom of too little fiber? “Dull skin,” Peterson says. And research on the gut-skin axis furthers this concept. The idea is that your gut and skin microbiomes are related, so what’s good for one is good for the other—and vice versa. Studies suggest that fiber can help fight acne and heal wounds. Fiber also helps reduce inflammation, Davis points out, which is associated with a range of skin conditions, per the Cleveland Clinic.

High cholesterol

Fiber helps your body get rid of excess cholesterol. “[So] inadequate fiber intake may make it harder to manage healthy cholesterol levels,” Barrett explains. This is more likely to affect you if you already have high cholesterol, or if your diet is high in saturated and trans fats, which can lead to high cholesterol, per the Mayo Clinic.

Low energy

If you feel tired on and off or find yourself crashing after lunch, pay attention to what you’re putting on your plate. “Fiber’s other role is helping to stabilize blood sugar levels,” Landry says. “So someone who doesn’t consume a lot of fiber might experience energy crashes throughout the day because of spikes and drops in their blood sugar.”

Constantly getting sick

Immune cells are distributed throughout your body, but 80% of them live in your gut, per the Cleveland Clinic. And since fiber keeps your gut healthy, it shouldn’t surprise you to learn it plays a role in your immune system. “Fiber feeds the good gut bacteria that produce anti-inflammatory compounds and strengthen the immune system,” Davis explains. So if you’re getting sick more often or struggling to shake that cold, check your fiber intake—you may need more.

How to get more fiber in your diet

Thankfully, upping your fiber intake is easy: Start eating more high-fiber foods. “Aim to include at least one fiber-rich food at every meal, such as berries at breakfast, beans at lunch, and a veggie side at dinner,” says Amy Davis, R.D.N., Live Conscious nutrition consultant. And start slowly—too much fiber too fast can upset your stomach, explains Matt Landry, Ph.D., R.D.N., assistant professor at UC Irvine Joe C. Wen School of Population & Public Health.

Related Stories