If you’ve spent any time on social media lately, you’ve probably seen someone telling you to eat 100 grams of fiber a day. Meanwhile, the average American is getting about 15. The truth sits somewhere in between, and the people who’ve figured out how to handle it best might surprise you: professional athletes.
Fibermaxxing gets one big thing right, and it’s worth saying up front, however it also gets a couple of things wrong, and those are the parts that can leave you feeling worse than when you started.
What fibermaxxing gets right
Most people really do need more fiber, and not by a little. Fiber is one of the most underrated parts of a healthy diet. It keeps you full longer, it feeds the bacteria in your gut, and it slows down how quickly carbohydrates hit your bloodstream, which means steadier energy and fewer crashes through the day. Over decades of research, people who eat more fiber consistently have lower rates of heart disease, type 2 diabetes, and early death.
If protein is what builds the body, fiber is a big part of what keeps the whole system running efficiently.
How much you actually need
The general target is about 25 grams a day for women and 38 grams for men, which works out to roughly 14 grams for every 1,000 calories you eat. Most people are getting less than half of that, so if the trend is nudging you to eat more beans, vegetables, and whole grains, it’s pointing you in the right direction.
Where it goes wrong: too much, too fast
What a lot of these videos and posts skip is that your body needs time to adjust. I like to think of the gut like a muscle. You wouldn’t walk into a gym for the first time and try to max out your squat, and your gut works the same way. If it hasn’t been trained to handle a lot of fiber, jumping from 15 grams to 60 overnight isn’t going to make you healthier. It’s going to leave you bloated, gassy, and uncomfortable, and most people quit right there.
There are a few other things worth knowing. Fiber powders can help fill a gap, but they aren’t a replacement for the real thing, because a scoop of psyllium doesn’t give you everything that beans, vegetables, and whole grains do. Fiber also needs water to do its job, so adding more fiber without drinking more tends to make digestion harder, not easier, and more isn’t endlessly better. Very high intakes can interfere with how you absorb certain minerals and medications, and there’s no evidence that 100 grams a day does anything 35 grams doesn’t.
The better approach is to build up gradually. Add a few grams a week, drink more water as you go, and give your gut time to adapt, and train.
Where it goes wrong: timing
This is where my work with athletes comes in, and it’s the part of the conversation almost nobody is having.
On training and recovery days, my athletes eat plenty of fiber. Their meals are built around beans, vegetables, whole grains, and fruit. But on the morning of a game, fiber comes way down, and there’s a good reason for it.
Fiber slows gastric emptying, the speed at which food moves out of your stomach. On a normal day, that’s a good thing, because it keeps you full and keeps your blood sugar steady. On game day, it becomes a liability. When food is sitting in your stomach while your body is trying to perform at its highest level, it can lead to bloating, cramping, diarrhea, and general discomfort, especially in anything that lasts longer than an hour. So the plate changes. Fiber goes down, easy-to-digest carbs and lean protein go up, and once the game is over, the vegetables and beans come right back.
That’s the real lesson here. Fiber isn’t something you max out. It’s something you manage, depending on what your body needs.
And you don’t need to be playing on Sunday for this to apply to you. If you have a long run, a race, a big hike, or even an early, hard workout, you’ll probably feel better keeping the meal right before it on the lighter side when it comes to fiber.
What the evidence says & What it doesn’t.
What it says:
Higher fiber intake is strongly linked to lower risk of heart disease, type 2 diabetes, colon cancer, and early death, with benefits showing up at 25 to 29 grams a day and continuing above that.
Most adults fall well short of the recommended intake.
Fiber slows digestion and helps blunt blood sugar spikes after meals.
Sports nutrition guidelines recommend lower-fiber meals before competition to reduce the risk of stomach trouble.
What it doesn’t:
There’s no evidence that extreme intakes like 100 grams a day offer extra benefit, and there are real reasons to think they can cause problems.
Fiber supplements don’t fully replace the benefits of fiber from whole foods.
Tolerance varies from person to person. Some athletes handle more fiber before training than others, so test it during practice, never on game day.
If you have IBS, IBD, or another digestive condition, talk to your doctor or a dietitian before making big changes.
On the plate
Here are two days side by side, one built for a normal training day and one built for the morning of a game.
Training day: about 35 to 40 grams of fiber
Breakfast: overnight oats (about 12 g). Half a cup of oats soaked overnight with Greek yogurt and milk, finished with a tablespoon of chia seeds and half a cup of raspberries.
Lunch: stewed black beans with roasted chicken (about 15 g). Slow-stewed black beans with roasted chicken, sautéed peppers and onions, fresh corn salsa, and a handful of cilantro.
Dinner: seared salmon over farro (about 10 g). Crispy-skinned salmon over warm farro with roasted Brussels sprouts, pomegranate seeds, and crushed pistachios.
If you want to switch things up, a red lentil curry with roasted cauliflower and brown basmati rice works as either lunch or dinner, and it’s one of the easiest ways I know to add 15 grams of fiber to your day.
Game-day morning: under 5 grams of fiber
Pre-game breakfast. Egg whites, a small portion of sautéed spinach, turkey bacon, and a roasted sweet potato, skin off, with a spoonful of peanut butter.
There’s enough protein to keep you steady and enough carbohydrate to fuel the work, with so little fiber that your stomach stays out of the way. The beans and Brussels sprouts come back after the final whistle.
The bottom line
Fibermaxxing is half right. You’re probably not eating as much fiber as you should, and getting more of it from real food is one of the best things you can do for your health. But more isn’t the goal on its own. Build up slowly, get it from your plate rather than a powder, and know when to pull back.
Enough, at the right time. That’s the move.
Read next: How Much Protein You Really Need, and What Else Matters
Follow the work at @ironveil_co, or reach out through the Contact page.
This post is for general education and is not medical advice. Talk to your healthcare provider before making significant changes to your diet.
References
Reynolds A, et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. 2019;393(10170):434-445.
Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press; 2005.
Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement: Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016;48(3):543-568.
de Oliveira EP, Burini RC, Jeukendrup A. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med. 2014;44(Suppl 1):S79-S85.
Quagliani D, Felt-Gunderson P. Closing America’s fiber intake gap. Am J Lifestyle Med. 2017;11(1):80-85.