Fiber is the new protein — at least on social media, where TikTokers, Instagrammers and other creators are embracing “fibermaxxing.”
The idea is simple: Eat more fiber.
And most Americans could use more of it. Researchers estimate that only about 5% of U.S. adults get the recommended daily amount of fiber, a type of carbohydrate that passes through the digestive system largely undigested, helping keep bowel movements regular. Its benefits extend beyond the bathroom: Certain types can help lower cholesterol, manage blood sugar and feed beneficial gut bacteria.
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Dietitians welcome the newfound attention to fiber. But Yasi Ansari, a registered dietitian, said the “maxxing” mindset can turn a healthy goal into a push to eat more than your body needs.
Fibermaxxing is the latest in a social media fascination with “maxxing,” or taking self-improvement to the limit. Previous iterations of the trend have included “proteinmaxxing,” “sleepmaxxing” and “looksmaxxing.” The catchy hashtags and deluge of attention on specific health topics can draw attention to everyday habits, but can push things beyond the science.
“The idea shouldn’t be to max out our nutrition,” she said. “It should be: How do we meet our needs in the best way to support our health and make sure that it’s not taking away from other nutrients?”
Joanne Slavin, a professor of food science and nutrition at the University of Minnesota Twin Cities, was initially worried fibermaxxing would encourage people to overdo it. But she also sees an opportunity to address a longstanding dietary gap.
“We have enough research to know we need more fiber,” Slavin said.
What is fiber, and why do we need it?
Fiber occurs naturally in plant foods such as beans, lentils, whole grains, fruits, vegetables, nuts and seeds. There are different types of fiber that do different jobs, and many foods contain a mixture.
Soluble fiber dissolves in water. Some forms create a gel that slows digestion and helps you feel fuller for longer. Some — though not all — soluble fibers help manage blood sugar levels and lower cholesterol. Soluble fibers can be found in foods like oats, beans, lentils, chia seeds, apples and the psyllium husk powder supplement you might find on grocery store shelves, Ansari explained.
Insoluble fiber, on the other hand, does not dissolve in water and primarily helps add bulk to stool, making waste easier to move through the intestines.
“It’s really great when it comes to constipation,” Ansari said. Sources of insoluble fiber include brown rice, nuts, seeds and many vegetables. A lot of foods contain both soluble and insoluble fiber.
In the large intestine, different types of gut bacteria break down different types of fiber, producing substances called short-chain fatty acids. One, called butyrate, provides fuel for the cells lining the colon. Eating a variety of fiber-rich foods helps feed a diverse community of beneficial gut bacteria, which supports overall health, Ansari said.
Diets higher in fiber are associated with lower risks of heart disease, Type 2 diabetes and colorectal cancer.
However, Slavin cautioned that people who eat more fiber often also eat a wider variety of plant foods and have healthier diets overall. Some of the benefits linked to higher fiber intake may come from that broader eating pattern, including the vitamins, minerals and other compounds those foods provide.
How much fiber should people eat?
A common benchmark for daily fiber intake is 14 grams for every 1,000 calories eaten. For someone eating 2,000 calories a day, that works out to 28 grams, which is the daily value used on nutrition facts labels.
Slavin said the recommendation grew out of studies that followed people’s eating habits and health over time. In the research she described, people in the highest fiber-intake group ate around 28 grams daily and had substantially lower cardiovascular disease risk than those eating the least.
“With the highest intakes of fiber,” she said, researchers saw “a 25% decreased risk of cardiovascular disease.”
That finding shows an association, rather than proving fiber alone caused the difference. It also does not establish 28 grams as a ceiling beyond which there are no further benefits.
The National Academy of Medicine recommends 25 grams of fiber a day for women and 38 grams for men ages 19 to 50. For adults 51 and older, the recommended amounts are 21 grams for women and 30 grams for men. Those differences largely reflect calorie needs, Slavin explained.
“I say let’s start with 28 and get people up to that,” she said.
Slavin estimates that typical intake is around 15 grams a day, leaving considerable room for improvement.
Can you have too much fiber?
While there is no established upper limit for daily fiber intake, that does not mean unlimited amounts are safe or helpful for everyone.
Increasing intake too quickly can cause gas, bloating, cramps or changes in bowel movements. Slavin said some people with certain digestive conditions may face more serious problems, such as fecal impaction, when a mass of hard stool becomes stuck and cannot pass normally. Those individuals should seek individualized advice before substantially increasing their fiber intake.
Too much fiber can also leave people too full to consume enough calories and other nutrients, including protein and fat, Ansari said.
“We get too full, and then we can’t meet our needs for the rest of the day,” she said.
That is particularly important for people who are malnourished or recovering from an eating disorder, she added. Overloading on fiber can make it harder to eat enough to meet their nutritional needs.
The right amount also depends on someone’s symptoms. For example, Ansari sometimes recommends certain soluble fibers to help absorb water and give loose stools more form. But she generally encourages clients to meet recommended fiber targets rather than push far beyond them.
“Don’t go zero to 100, aka don’t max,” she said. Ansari recommends increasing fiber intake by about 5 grams every week.
As you increase your fiber intake, make sure you’re drinking enough water, Ansari said. Fluids help fiber move through the digestive tract and keep stools softer and easier to pass. She generally recommends about 2 to 3 liters of fluids a day for women and 3 to 4 liters for men, though individual needs depend on body size, activity level and medical conditions.
What could a fiber-rich day look like?
For those looking to increase their fiber intake, Slavin and Ansari both recommended slowly incorporating higher-fiber options into your diet.
“Start with getting more fiber at each meal and each snack,” Ansari said. “You can do that by aiming for at least 3 to 5 grams of fiber per snack or meal.”
Slavin suggested making some simple swaps like whole-grain bread over white bread or adding beans to a soup or salad.
Breakfast could be oatmeal topped with berries, nuts or seeds. At lunch, try a sandwich on whole-grain bread with vegetables and a side of fruit. Dinner might include lentil soup or beans alongside brown rice and vegetables.
Snacks can contribute, too. Try whole-wheat crackers with hummus, popcorn with a piece of fruit or vegetables with a bean dip. Sprinkling chia seeds or ground flaxseed into oatmeal, cereal or a smoothie is another way to add fiber, Ansari said.
Some foods provide less fiber than people might expect. Lettuce, for example, is mostly water, Slavin noted, so a salad built mainly from lettuce may contribute relatively little. Adding beans, chickpeas, nuts or seeds can increase its fiber content. For comparison, a half-cup of cooked lentils provides about 8 grams of fiber, while a half-cup of raspberries provides about 4 grams.
Both dietitians emphasized variety. Eating a mix of whole grains, legumes, fruits, vegetables, nuts and seeds supplies different fibers along with other nutrients.
Convenient options count, too. Frozen vegetables, canned beans and dried fruit all contribute fiber, Slavin said. Blending whole fruits and vegetables into a smoothie also retains their fiber, as long as you do not strain out the pulp.
Slavin stressed finding easy, enjoyable ways to add fiber to your usual diet. People are less likely to stick with routines that become a chore.
Fiber supplements can help fill gaps and may help address specific problems, such as constipation, depending on the ingredient and the person’s needs, Ansari said. But they do not replace the vitamins, minerals and other beneficial plant compounds that come with eating a variety of fiber-rich foods.
“I would say food first, then fill any gaps with the supplementation,” she said.
For Slavin, fibermaxxing’s value is in getting people to pay attention to something their diets have long lacked.
“If this gets people to get more fiber into their diet, I believe there will be health benefits,” she said.
Ansari’s message is that getting enough matters more than pushing intake to extremes.
“You do not need to max to get all the benefits from fiber,” she said.
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