Overview of Should you be fibermaxxing? Here's what the science says
NPR’s Short Wave explores the social-media trend of “fibermaxxing” and the science behind fiber’s real health benefits, risks, and best practices. The episode features UCLA gastroenterologist Dr. Berkeley Limketkai, who explains that most Americans do not get enough fiber, but also warns that suddenly pushing intake very high can backfire. The core message: fiber is beneficial, but more is not always better.
Why fiber matters
Fiber is a carbohydrate the body can’t digest, but it still plays an important role in health:
- Improves bowel regularity by affecting stool consistency and transit time
- Supports the gut microbiome
- Helps produce anti-inflammatory molecules through microbial fermentation
- May contribute to broader health benefits when eaten as part of whole foods
The episode notes that over 90% of Americans don’t get enough fiber, with the average intake around 10–15 grams per day, well below recommended levels.
Types of fiber and what they do
Soluble vs. insoluble fiber
The episode walks through the main categories of fiber:
- Soluble fiber dissolves in liquid and forms a gel-like substance. It can help regulate stool and is often useful for people with looser stools or diarrhea.
- Insoluble fiber does not dissolve well, adds bulk, and generally helps move things through the digestive tract, making it more helpful for constipation.
Prebiotic fiber
- Prebiotics are largely plant-based fibers that feed beneficial gut bacteria.
- They overlap heavily with dietary fiber, though not all plant fibers are the same or equally helpful in every context.
Best ways to increase fiber safely
Dr. Limketkai recommends getting more fiber through whole foods first, especially:
- Fruits and vegetables
- Whole grains
- A varied diet that includes “the colors of the rainbow” to improve micronutrient diversity
Why whole foods are preferred:
- They provide fiber plus other beneficial compounds
- Fruits and vegetables also contain polyphenols, which may have anti-inflammatory, antioxidant, and anti-cancer effects
- Whole grains offer additional nutritional advantages beyond fiber alone
Fiber supplements can still be useful, especially in clinical settings, but they lack the full package of nutrients found in whole foods.
Fiber supplements, prebiotic drinks, and “fibermaxxing”
The episode takes a skeptical look at the booming market for fiber-added products and prebiotic sodas.
Main point:
- Adding fiber to a product does not automatically make it healthy
- If the rest of the product is still high in sugar, ultra-processed ingredients, or otherwise unhealthy, the fiber claim may be misleading
So while supplements and fortified foods can help people meet their needs, they are not a substitute for a generally healthy diet.
Can you eat too much fiber?
Yes—especially if you suddenly jump from a low-fiber diet to extremely high levels like 70–90 grams per day.
Potential downsides include:
- Bloating
- Abdominal cramping or pain
- Constipation or diarrhea
- Changes or disruption in bowel habits
- Possible interference with absorption of minerals like calcium, iron, and zinc
- In extreme cases, poor nutrient intake or malnutrition
The episode emphasizes that some populations do eat very high-fiber diets habitually, but that doesn’t mean a sudden “fibermaxxing” approach is right for everyone.
Practical takeaway
The best advice from the episode is to be intentional and gradual:
- Increase fiber slowly
- Favor whole foods over products merely fortified with fiber
- Stay within recommended intake ranges
- If you want to increase a lot, consider talking with a dietitian or nutritionist
- Pay attention to your body; if symptoms worsen, scale back
Bottom line
Fiber is clearly important, but the episode’s main lesson is that moderation and personalization matter. The healthiest approach is not to chase the highest possible number—it’s to build a balanced, sustainable fiber intake that fits your body and your overall diet.