The vast majority of us aren’t getting enough fiber in our diet, which can lead to a number of health issues down the road. Experts share exactly how much fiber you need, how to incorporate more of it, and how eating fiber might help with your weight-loss goals.
Many people understand the importance of eating protein as part of a healthy diet, yet they often neglect their fiber intake, which is vital for satisfying hunger and balancing blood sugar levels. If you’re in the camp where you could use a little help with your fiber intake, you’re not alone.
In fact, about 95 percent of Americans don’t get enough fiber each day, says Nichole Dandrea-Russert, a registered dietitian and author of The Fiber Effect. Most people only get about 15 grams of fiber daily out of the recommended 25 to 38 grams per day, according to a study published in May 2013 in the journal Advances in Nutrition.
That said, increasing your fiber intake is a very attainable goal. And once you’re on the right track, it can help alleviate and even prevent a bevy of health issues.
If you’re looking to increase fiber in your diet, aim to eat more vegetables, fruits, whole grains, and beans and legumes.
“Increasing intake of various plant-based foods [where you will find the most fiber] can help folks get various types of fiber to improve health outcomes, like decreasing constipation and inflammation that may lead to lifestyle diseases, such as cardiovascular disease, diabetes, certain types of cancer, and autoimmune diseases,” Dandrea-Russert says.
Read on to learn more about fiber, its benefits, and how to successfully make it a mainstay of your diet.
What Is Fiber?
Dietary fiber is a type of carbohydrate found in plant-based foods, such as vegetables, fruits, and whole grains. Unlike other carbohydrates, protein, and fat, your body can’t digest fiber, so it passes through your body in its whole form.
There are two main types of fiber: soluble and insoluble. Soluble fiber is responsible for lowering cholesterol, balancing blood sugar levels, and feeding beneficial gut bacteria.
Soluble fiber comes in viscous and nonviscous forms. Viscous soluble fiber absorbs water and forms a gel. This type of fiber slows the release of sugar into the bloodstream and excretes excess cholesterol, says Dandrea-Russert.
Nonviscous soluble fiber, or fermentable fiber, doesn’t form a gel and moves smoothly through the digestive tract, where it then serves as a prebiotic — a source of food — for the gut bacteria in your colon, explains Kara Landau, a registered dietitian at Gut Feeling Consultancy and nutrition advisor to the Global Prebiotic Association.
The byproduct of this fermentation is short-chain fatty acids, says functional gut health dietitian Paulina Lee. Short-chain fatty acids help reduce overall inflammation, keep your gut’s pH levels in check, and decrease oxidative stress, which can help fend off disease. Some examples of high-soluble-fiber foods are beans, oats, asparagus, sweet potatoes, pears, and apples.
Insoluble fiber, on the other hand, doesn’t dissolve in water like soluble fiber does, and adds bulk to your stool, keeping you regular. Wheat bran, nuts, seeds, beans, and vegetables like green beans and cauliflower are all excellent sources of insoluble fiber.
“[Insoluble fiber] passes through like a broom, bringing any toxins with it, speeding up the digestion of food, increasing stool bulk, and preventing constipation,” Dandrea-Russert says.
Interested in learning more? Check out The Fiber Effect to Heal the Body
What Is the Recommended Fiber Intake?
Just as caloric recommendations vary by age and gender, so does fiber intake.
The Dietary Guidelines for Americans recommends 14 grams of fiber for every 1,000 calories you consume, so women should aim to get about 25 grams of fiber daily, and men, 38 grams daily, explains Christine Lothen-Kline, MPH, RD, dietitian director with ModifyHealth.
“Generally speaking, a 30-year-old woman who is not trying to lose weight would need approximately 2,000 calories and 28 grams of fiber daily, while a man of the same age would need closer to 2,400 calories and 34 grams of fiber,” says Lothen-Kline. “Our need for fiber does decrease somewhat as we age, but this is mostly due to our calorie intake decreasing as well.”
Is Resistant Starch a Fiber?
Resistant starch is sometimes referred to as a third type of fiber, Landau says. Resistant starch passes through your body whole until it reaches the colon, where it then becomes food for probiotics (the good bacteria).
"Resistant starch is able to reach the deepest part of your colon, where it acts as a source of energy for the probiotics [or the live cultures of bacteria] and provides a strong prebiotic effect,” says Landau. “Resistant starch has been shown to make your cells more responsive to insulin, resulting in better blood-sugar-level management, as well as imparting a feeling of fullness when consumed together with protein.” That fullness may also lead to you eating less at a meal, the expert adds, so it can be helpful for weight management, too.
Some examples of resistant starches are overnight or raw oats, green bananas, and rice that’s been cooked and then cooled. During the cooling process, starch molecules change their structure, which causes them to become more resistant to digestive enzymes and allows them to become a fuel source for gut bacteria, Landau explains.
Consuming a balanced blend of foods with soluble and insoluble fiber and resistant starch is key to healthy digestion and overall health. If you’re dealing with constipation, for example, you don’t want to overload your digestive tract with insoluble fiber alone.
“We have to be careful, because if we are already dealing with constipation, and we eat a lot of insoluble fiber [think: bran cereals], we can end up creating a traffic jam and make things worse,” says Lothen-Kline.
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What Are the Best High-Fiber Foods?
If you’re looking to increase fiber in your diet, aim to eat more vegetables, fruits, whole grains, and beans and legumes.
“Fiber is only found in plant-based foods, not in animal products like eggs, dairy, meat, fish, or poultry,” says Dandrea-Russert. “Therefore, eating a wide variety of plant-based foods is key to getting enough fiber and various types of fiber.”
Loading up on foods that have a combination of soluble and insoluble fiber is ideal. For example, avocado is made up of 75 percent insoluble fiber and 25 percent soluble fiber. Sweet potatoes are also a prime pick at 50/50 insoluble and soluble fibers.
Other foods that shine in the fiber department include legumes, which contain both soluble and insoluble fiber along with plenty of protein, and berries. For extra soluble fiber, snack on apples, carrots, nuts, and seeds. To pack in more insoluble fiber, incorporate wheat brain, tempeh, dark leafy greens (such as kale), and cruciferous veggies, such as broccoli and cauliflower, into your diet.
When shopping for grain products, look closely at the ingredients list and choose options made of “whole grains” or “whole wheat.” White flour and white potatoes are a major source of most Americans’ fiber intake, but because they undergo a refining process, they’re stripped of essential nutrients (unless added back in) and have lower fiber content compared to whole grains, Dandrea-Russert says.
Depending on the brand, one slice of white bread may offer only 1 gram of fiber, while one slice of whole-grain bread may have 3, 4, or even 5 grams of fiber per slice.
Quinoa, amaranth, barley, and sorghum are other types of whole grains that also provide insoluble fiber.
Those who may have difficulty passing fiber can opt for a more minimally processed flour, such as a legume or nut flour, Dandrea-Russert says. But remember, eating foods in their whole form, like whole almonds instead of almond flour, is best for optimal nutrition. This is because your body takes a longer time to digest whole foods, which helps create more balanced blood sugar levels.
Does Fiber Help or Hurt Protein Absorption?
Insoluble fiber, such as wheat bran, may affect protein absorption, though it’s typically only by 10 to 15 percent, says Dandrea-Russert. “Fiber may bind to some protein, making it unavailable for digestion and usage by our bodies,” she explains.
Because of this, vegans and vegetarians adhering to a plant-based diet may want to increase their protein intake by 10 to 15 percent to compensate for any protein loss due to fiber.
For example, if a 150-pound person typically needs 55 grams of protein each day (based on the recommended daily amount), shifting that amount to 60 grams of protein to make up for that 10 percent of unabsorbed protein would be ideal, Dandrea-Russert says. This can be easily accomplished with an extra 2 tablespoons of hemp seeds or ½ cup of lentils, for instance.
Can Fiber Help With Weight Loss?
Research says yes. According to a study published in October 2019 in The Journal of Nutrition, fiber was the strongest predictor of weight loss. Participants followed a low-calorie diet, but those who consumed at least 25 grams of fiber each day lost an additional 3 pounds over the course of six months.
Fiber’s ability to enhance the diversity of bacteria in our gut microbiome aids with weight loss as well, per a study published in July 2017 in the International Journal of Obesity.
Short-chain fatty acids from fiber fermentation in the gut also helps regulate metabolism and can promote the release of the hormones PYY and GLP-1, which signal that we’re full, says Dandrea-Russert.
Fiber — especially soluble fiber — is effective for weight loss and weight maintenance because it fills you up and keeps you fuller longer. “This helps minimize overeating, and while more research is needed, it may also help minimize excess caloric intake in subsequent meals,” Dandrea-Russert says.
Another major benefit of fiber is its ability to regulate blood sugar levels by helping decrease insulin production, which discourages fat storage in the body.
“Fiber helps to regulate blood sugar levels, which allows us to use the sugar from food as energy over a period of time instead of excess sugar entering into the bloodstream at once,” says Dandrea-Russert. “Excess sugar in the bloodstream can lead to more insulin secretion, which brings sugar from our bloodstream to our cells for energy use. However, insulin is also a fat storage hormone and promotes fat storage when excess sugar is present.”
Having said that, you don’t need to eat an exorbitant amount of fiber to shed pounds. While some research suggests that increasing fiber intake to at least 30 grams a day helps with weight loss, aiming to get the daily recommendation of 25 grams (for women) seems to be just as effective, says Lothen-Kline.
How to Safely Increase Fiber in Your Diet
If your diet could use a fiber boost, go slow and be patient when adding it in.
“Jumping from eating 15 grams of fiber to 30 grams overnight may cause digestive discomfort, like bloating and gas, because our gut microbiome needs time to adjust to the change in fiber intake,” says Lee. “This isn’t dangerous. It’s more uncomfortable. To avoid discomfort, make a small change in your eating habits each week.”
Lee suggests starting with fiber-food swaps. For example, opt for whole-grain or whole-wheat bread and pasta over their white-flour alternatives. Instead of potato chips or crackers, stock your snack arsenal with nuts, fruit, veggies, and rice cakes.
Another strategy is to add whole grains, like barley or quinoa, to your soups and salads. And prioritize plant-based sides by filling at least half of your plate with non-starchy vegetables, Lee adds.
Breakfast is a prime opportunity to get a jump-start on your fiber intake for the day. Lothen-Kline encourages adding nuts and berries to oatmeal, and adding vegetables like onions, peppers, and spinach to eggs.
Creating weekly meal plans filled with fiber-rich foods will help you stay on track. Try the “Meatless Monday” approach of incorporating a few more plant-based dishes into the week. For example, replace meat in tacos or soups with beans, Lothen-Kline suggests.
Beans are particularly high in fiber, so if they’re new to your diet, adding them gradually is key. Start with just a few tablespoons at first, advises Dandrea-Russert. Once you can tolerate that amount (meaning you aren’t feeling overly gassy or bloated from it, although a little gassiness is normal, she says), try a little more next time.
If you’re trying other new fiber-rich foods, make sure you only incorporate one or two at a time. If you do well with those, add one or two more the following week.
“It can take your body some time to adapt to the various types of fiber,” says Dandrea-Russert. “This is not necessarily a bad thing as you’re waking up the healthy bacteria in your gut.”
One final pro tip: Drink lots of water! “Since fiber moves through our bodies whole, we need water to help push it through,” Dandrea-Russert says. Divide your body weight in half for an estimate of how many ounces of water you need to drink each day to help your new fiber goals succeed.
Getting enough fiber may feel daunting at first, but with the right changes to your diet, you can gradually increase your daily intake. Start small, pay attention to nutrition labels, make food swaps, hydrate, and you’ll reach your goal in no time.
