Should you be fibermaxxing? Here's what the science says

Summary

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Podcast Summary: Should You Be Fibermaxxing? Here’s What the Science Says

Podcast: Short Wave (NPR)
Host: Emily Kwong
Guest: Dr. Berkeley Limket Kai, Gastroenterologist at UCLA
Air Date: May 13, 2026
Duration: ~15 minutes

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Episode Overview

This Short Wave episode dives into the online phenomenon of “fibermaxxing”—the trend of aggressively increasing fiber intake. Host Emily Kwong and guest Dr. Berkeley Limket Kai unpack the science behind fiber in our diets, discuss the risks and benefits of “maxxing” out on fiber, and offer practical advice for finding the “Goldilocks” amount that’s just right for your individual needs, all with a touch of humor and clear, relatable explanations.

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Key Discussion Points & Insights

1. The "Fibermaxxing" Trend & Why It Matters

• [00:17-01:00]
  • Emily introduces the “maxxing” trend seen on social media (looks, gym, protein, and now, fiber).
  • "Over 90% of people in the US don’t get enough fiber." (Emily Kwong, 00:42)
  • Dr. Kai confirms, citing the “standard American diet” as fiber-poor and full of refined, processed, and fatty foods.

2. How Much Fiber Do We Actually Need?

• [01:32-02:43]
  • The average American consumes just 10-15g per day; recommended is “more than double that.”
  • Insufficient fiber leads to constipation, straining, incomplete evacuation, and irregularity.
  • "When they don't consume enough fiber, they tend to have more constipation..." (Dr. Kai, 01:49)

3. Is More Always Better?

• [02:29-02:43]
  • "Increasing fiber is generally a good thing... but too much of any good thing can lead to detriments." (Dr. Kai, 02:29)
  • The aim is balance, not just quantity.

4. What is Fiber, and Why Does It Matter?

• [04:23-05:05]
  • Fiber is a carb that isn’t digestible by our bodies.
  • Benefits split into two main categories:
    • Mechanical: Affects bowel habits.
    • Functional: Feeds gut bacteria, shapes microbiome, generates anti-inflammatory molecules.
  • "It does a lot, actually—fiber." (Emily Kwong, 05:03)

5. Soluble vs. Insoluble vs. Prebiotic Fiber

• [05:07-07:09]
  • Soluble fiber: Dissolves in water, forms gels, helps diarrhea and loose stools.
    • "Soluble fibers... can actually help form a gel of the stool." (Dr. Kai, 05:52)
  • Insoluble fiber: Doesn’t dissolve in water, draws in liquid, helps constipation.
    • "Insoluble fibers...lead to more liquefaction of the stools." (Dr. Kai, 06:10)
  • Prebiotic fiber: Mostly synonymous with dietary fiber; prebiotics feed beneficial bacteria.
    • "The predominant form of prebiotics actually come in the form of plant fibers." (Dr. Kai, 06:43)
  • Not all plant fibers are edible (e.g., tree leaves).

6. How to Increase Fiber—Safely

• [07:10-08:14]
  • Eat more fruits and vegetables (ideally a variety—the “colors of the rainbow”).
  • Benefits: Not just fiber, but also polyphenols (anti-inflammatory, antioxidant, anti-cancer).
    • "We would actually also recommend eating the colors of the rainbow." (Dr. Kai, 07:57)
  • Whole grains are highly recommended for fiber (and healthy fats).

7. Fiber Supplements & Prebiotic Sodas

• [08:33-09:31]
  • Supplements: Useful, especially for those needing a boost.
    • "Fiber supplements are actually beneficial and a good source of fiber intake." (Dr. Kai, 08:42)
  • Downside: Lack other nutrients found in whole foods.
    • "It does not contain all those other nutrients or beneficial molecules that natural fiber in whole foods contains." (Dr. Kai, 08:56)
  • Caution with prebiotic sodas: Added fiber doesn’t automatically make a product healthy if the rest of its ingredients are not beneficial.
    • "If the other components...actually does the complete opposite, then it's not really that beneficial..." (Dr. Kai, 09:31)

8. The Risks of ‘Fibermaxxing’

• [09:59-11:04]
  • Drastic increases (70-90g/day) possible in some cultures/vegans, but risky if not done gradually.
  • Sudden increase can cause bowel changes, microbiome disruption, and even problems with absorption of minerals (calcium, iron, zinc) or trigger malnutrition.
    • "Someone...who suddenly ramps up to 70 to 90 grams per day could experience a lot of adverse effects from such high fiber intake." (Dr. Kai, 10:16)

9. Expert Guidance: How to Find What’s ‘Just Right’

• [11:04-12:27]
  • Gradually increase fiber, ideally with a dietitian/nutritionist's help.
  • Listen to your body—look for cramping, bloating, changes in habits as signals to slow down.
    • "Start low and ramp up. Stay within the recommended guidelines..." (Dr. Kai, 11:09)
  • Moderation and personalization matter—what works isn’t universal.
    • “What works for you might not work for your friend.” (Emily Kwong, 12:01)

10. The Overall Message

• [12:27-12:49]
  • "Life is a balance, and too much of any good thing can actually sometimes be harmful." (Dr. Kai, 12:27)
  • Judicious, intentional, and strategic increases are best—optimize health in one area without sacrificing another.

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Memorable Quotes

• Emily Kwong [00:42]: “Over 90% of people in the US don’t get enough fiber.”
• Dr. Berkeley Limket Kai [01:49]: “When they don't consume enough fiber, they tend to have more constipation...”
• Dr. Berkeley Limket Kai [02:29]: “Increasing fiber is generally a good thing... but too much of any good thing can lead to detriments...”
• Dr. Berkeley Limket Kai [05:52]: “Soluble fibers...help form a gel of the stool...helpful for individuals who tend to have looser stools or more diarrhea.”
• Dr. Berkeley Limket Kai [06:10]: “Insoluble fibers...draw more liquid into the intestines...helpful for individuals who tend to have a more constipation-like bowel habit.”
• Emily Kwong [12:01]: "What works for you might not work for your friend. Is that the overall message for you?"
• Dr. Berkeley Limket Kai [12:27]: “Life is a balance, and too much of any good thing can actually sometimes be harmful.”

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Important Timestamps for Reference

• 00:17 — Emily introduces “fibermaxxing” as an online trend.
• 01:00 — Dr. Kai on why Americans are fiber-deficient.
• 01:32 — The average fiber intake vs. recommendations; bowel effects.
• 02:29 — Benefits and limits of increasing fiber.
• 04:35 — Benefits of fiber: mechanical and microbiome effects.
• 05:52 — Soluble vs. insoluble fiber explained.
• 07:20 — How to eat more fiber (fruits, vegetables, whole grains).
• 08:42 — Fiber supplements’ pros and cons.
• 09:31 — Caution about prebiotic sodas and processed products.
• 10:16 — The dangers of rapid “fibermaxxing.”
• 11:09 — Safe, gradual increase recommendations.
• 12:27 — The core message: moderation, balance, individualization.

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Final Takeaways

• Don’t ‘fibermaxx’ overnight: Sudden, extreme increases can be harmful.
• Whole foods > supplements: For broader nutrient benefit.
• Aim for gradual, personalized increases: Preferably with expert support.
• Balance and moderation are key: Too much of even a good thing can have negative consequences.

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For more science, creativity, and good humor, subscribe to Short Wave on your favorite app!

Transcript

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[Emily Kwong]

You're listening to Short Wave from npr. Shortwavers. Some people on our team are very online. I'm actually not one of them, but I have been alerted to this phenomenon on social media known as maxing. Whether that's looks maxing, gym maxing, protein maxing, or fiber maxing, I'm tired of not getting enough fiber in. So welcome to day one of becoming a Fiber Max. I'm fiber maxing. Hard fiber is officially scared of me now. For anybody trying to die, quit protein maxing, bro, and Fiber Max. I will say I've looked at some of these videos now and Fiber Maxers are right about one thing. Over 90% of people in the US don't get enough fiber.

[Dr. Berkeley Limket Kai]

The standard American diet, or the Western diet in general actually is very depleted of fiber.

[Emily Kwong]

This is Berkeley Limket Kai. He's a gastroenterologist at ucla and he says most Americans are fiber deficient because, well, we're eating a lot of other stuff.

[Dr. Berkeley Limket Kai]

We do like our refined carbohydrates, the sweets. We do love our fried and fatty foods. We do love our ultra processed foods which are intentionally created to be more attractive, tasty. And unfortunately, ever since being little children, folks don't really like eating their broccolis as much.

[Emily Kwong]

The Average person eats 10 to 15 grams of fiber per day, but the recommended daily average is more than double that number. And usually the place that makes itself known is the porcelain throne, the lavatory, the toilet.

[Dr. Berkeley Limket Kai]

When they don't consume enough fiber, they tend to have more constipation. And as such, you know, they could actually experience more straining when having bowel movements. They can feel like they're not completely evacuated after each toilet session. They could feel that the feeling of having a bowel movement is more extended or over time, or the interval between bowel movements may be longer. So those are some of the initial telltale signs of not having enough fiber intake.

[Emily Kwong]

I know what you're thinking. You're listening to this and saying short wave. You already did an episode on your pooping all wrong and now you're telling me I'm fibering all wrong. But maybe I'm saying you're fibering perhaps not enough. And we have answers for you.

[Dr. Berkeley Limket Kai]

Especially in the United States, increasing fiber is generally a good thing. Too much of Any good thing can lead to detriments to your health or your well being. But in general, yes, fiber is your friend.

[Emily Kwong]

Today on the show we're tackling fiber. We speak to a gastroenterologist to parse the science of how little is too little, how much is too much. And like Goldilocks, how do you know what's just right? I'm Emily Kwong and you're listening to Short Wave, the science podcast from npr.

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[Emily Kwong]

okay, I'm here with Berkeley Limkekai, a gastroenterologist, to talk about fiber. Fiber is a carb that our bodies cannot digest. Berkeley, can you talk about some of the benefits of fiber?

[Dr. Berkeley Limket Kai]

So I guess the way I look at fiber and its potential benefits are on one hand, the mechanical aspects of its effects, which leads to changes in bowel habits. And the other way is looking at it from the functional effects. So that's where on one hand it's able to shape the gut microbiome and at the same time serve as nutrients or raw materials for the microbiome to generate these anti inflammatory molecules.

[Emily Kwong]

Wow. That it does a lot actually fiber.

[Dr. Berkeley Limket Kai]

It does.

[Emily Kwong]

And do all forms of fiber do all the things? Because I know there's like soluble fiber versus insoluble fiber and then there's prebiotic fiber. So like what? What are all those types and what does what.

[Dr. Berkeley Limket Kai]

There are many different forms of fiber. There are nuanced differences between them that then actually Leads to a differential effect on the types of bacteria that they promote. And in terms of the types of molecules that they tend to be converted into. And there are also some types of fibers that, when consumed in disease states, may actually be detrimental to the body or actually be pro. Inflammatory, Paradoxically.

[Emily Kwong]

Yeah. And can you explain what is the difference between soluble and insoluble fibers?

[Dr. Berkeley Limket Kai]

Yeah, so soluble fibers are the types of fibers that, as the name implies, it dissolves in liquid. And so they can actually help form a gel of the stool or help kind of produce a stool mass. And these are more helpful for individuals who tend to have looser stools or more diarrhea. By contrast, insoluble fibers are not as well digested. As they pass through the gastrointestinal tract. They tend to draw more liqu into the intestines, thus leading to more liquefaction of the stools. And so these are more helpful for individuals who tend to have a more constipation like bowel habit.

[Emily Kwong]

What a power couple, that insoluble. Insoluble fiber. And then where does prebiotic fiber fit into this?

[Dr. Berkeley Limket Kai]

So the term prebiotic and dietary fibers are actually almost synonymous.

[Emily Kwong]

Oh, okay.

[Dr. Berkeley Limket Kai]

One could even theoretically consider them interchangeably. There are some nuanced differences, but the predominant form of prebiotics actually come in the form of plant fibers. Interestingly, not all plant fibers are dietary because there are leaves and trees outside your building or your home that you do, not necessarily.

[Emily Kwong]

That we cannot eat.

[Dr. Berkeley Limket Kai]

Exactly, exactly.

[Emily Kwong]

Yeah. So prebiotics are just plant fibers, and some are soluble and some are insoluble.

[Dr. Berkeley Limket Kai]

In general, yes.

[Emily Kwong]

Okay, okay, cool. Complicated. Well, then in that case, I want to know how people can increase their fiber safely. What's the best way to do that?

[Dr. Berkeley Limket Kai]

Yeah, one of the best ways to increase fiber in their diet is actually to increase the proportion of fruits and vegetables that they incorporate into their meals. And the reason for this is because on one hand, you know, there is the benefit of actually getting the fiber in these fiber rich foods, but at the same time, these particular food types actually also have these molecules called polyphenols that have anti inflammatory, antioxidant, native, and anti cancer effects. In addition to that, we would actually also recommend eating the colors of the rainbow. And that is you have different colored vegetables or fruits, you know, throughout the week. And the reason for that is because there are also other types of micronutrients and vitamins that actually then help balance out your diet and your micronutrient intake. If you actually have this kind of diversity of foods.

[Emily Kwong]

Awesome. So yeah, eating lots of fruits and vegetables, eating the rainbow. What about like whole grains? Does switching entirely to whole grains help with fiber intake?

[Dr. Berkeley Limket Kai]

Very much so. Whole grains are actually very rich in fiber and have a lot of beneficial money, unsaturated fats. So there are also other potential benefits from whole grains themselves.

[Emily Kwong]

Another way some people are trying to get fiber or fiber max is with supplements. There's also foods with fiber additives. What do you think of all that?

[Dr. Berkeley Limket Kai]

Yeah. So fiber supplements are actually beneficial and a good source of fiber intake. In clinic, we oftentimes recommend recommend fiber supplements for our patients. The supplements is an easy way of boosting daily fiber intake.

[Emily Kwong]

Gotcha.

[Dr. Berkeley Limket Kai]

The potential disadvantage of consuming a fiber supplement is that while it is a great source of fiber, it does not contain all those other nutrients or beneficial molecules that natural fiber in whole foods contains.

[Emily Kwong]

There is a benefit to the whole foods approach, and it's interesting because fiber, at least on the business side, like food brand watchers are saying fiber is going to be the next thing. There's a booming prebiotic soda market. So what do you think of these sodas? Are they a medically sound way of getting fiber or is it a scam?

[Dr. Berkeley Limket Kai]

It's a great question. One could use these different nutrients and add them to virtually any product and use that to increase the attractiveness of their product and maybe the health benefit profile of those products. However, if in totality, or if the other components of such product actually does the complete opposite, yeah, then it's not really that beneficial to consume in the first place. Even if there's something that can is said to be potentially beneficial.

[Emily Kwong]

So this, this kind of brings us back to fiber maxing, where people on social media are just trying to consume as much fiber as possible. Like the number is the point, 70 or 80 grams?

[Dr. Berkeley Limket Kai]

Yes.

[Emily Kwong]

the end of the day, what do you think about people eating that much fiber? Is it ever a good thing?

[Dr. Berkeley Limket Kai]

So 70 to 80 grams, or even 90 or even beyond that of fiber per day is not unprecedented. If you look at other cultures where they consume predominantly fruits and vegetables, or in those who are vegan, they already routinely consume a very high consumption of fiber per day. However, someone who is not really accustomed or adapted to consuming that high of a fiber intake and then suddenly ramps up to 70 to 90 grams per day could along the way experience a lot of kind of adverse effects from such high fiber intake. Alterations in our bowel habits, maybe disruption of the gut microbiome potentially could also cause compromise in certain micronutrient intake, such as calcium, iron and zinc, and also can lead to some degree of malnutrition.

[Emily Kwong]

Yeah. So what is the best way to increase your fiber intake but responsibly?

[Dr. Berkeley Limket Kai]

If one actually wanted to increase their fiber intake, I would actually recommend that they meet with a dietitian or nutritionist so they can actually look at kind of the overall balance of their diet to make sure that while, yes, they're increasing dietary fiber consumption, that they're not compromising then on other nutrients. You know, start low and ramp up. Stay within the recommended guidelines initially. And if one is able to then tolerate that amount of fiber, one could theoretically increase it thereafter, while keeping in mind that along the way, you know, if one were to develop, let's say, changes in their bowel habits or increased abdominal cramping, discomfort or pain or even feeling more bloating and distension, that it may be a sign to kind of down throttle kind of the increase in fiber, at least temporarily.

[Emily Kwong]

That sounds like very good advice because I feel like everything I'm learning from you is that moderation and intention are really important in diet and especially with fiber because it is such a delicate balance and also so much depends on the individual. What works for you might not work for your friend. Is that the overall message for you?

[Dr. Berkeley Limket Kai]

Very much so. Life is a balance, and too much of any good thing can actually sometimes be harmful. While one can still aim for increasing fiber intake, you also need to do that in judicious kind of intentional and strategic manner so that while optimizing your health in one area, you don't actually compromise your health in other areas.

[Emily Kwong]

Very important advice. Dr. Berkeley Limkett. Kai, thank you so much for talking to me about fiber and how to, you know, find that goldilocks middle with it.

[Dr. Berkeley Limket Kai]

Well, thank you very much for the invitation. It was a great pleasure chatting with you today,

[Emily Kwong]

Short Wavers. We've been doing a lot of health questions lately. If you have a question, write to us. Our email is shortshortwavepr.org we'd love to look into it. And while you're at it, follow us on whatever app you're listening to. This episode was produced by Hannah Chin. It was edited by Rebecca Ramirez. Tyler Jones checked the facts. Robert Rodriguez was the audio engineer. I'm Emily Kwong. Thank you for listening to Short Wave from npr.

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