Let’s talk about something that doesn’t get nearly enough attention in the fitness world: fiber. Macros, calories, and workouts get all the attention, but this topic matters more than most people realize, as it affects us in every way.
Colorectal cancer rates among Americans under 55 have been climbing by 1 to 2% every year. The American Cancer Society estimates that in 2026 alone, around 158,000 new cases of colon and rectal cancer will be diagnosed in the U.S. While researchers don’t have one single explanation, the usual suspects include sedentary lifestyles, heavy alcohol use, obesity, and low-fiber, high-fat diets loaded with processed foods. All of which we can actually control. Then, of course, there is a family history of colorectal cancer, which can be another contributing factor.
Here’s the kicker: only about 5% of Americans eat enough fiber each day. Women need around 25 grams daily (21 grams after 50), and men need about 38 grams (30 grams after 50). Most of us are getting less than half of that amount.
What Fiber Actually Does in Your Body
Fiber is a type of carbohydrate that your body cannot digest. Unlike other carbs that get broken down into glucose, fiber travels through your digestive system largely intact. That sounds simple, but what happens along the way is anything but.
High fiber intake has been consistently linked to a lower risk of:
- Coronary heart disease
- Stroke
- High blood pressure
- Type 2 diabetes
- Obesity
- Certain gastrointestinal conditions, including colorectal cancer
It also feeds your beneficial gut bacteria, helps regulate blood sugar, keeps you full longer, supports healthy cholesterol levels, and keeps things moving through your digestive tract.
If you’re someone who deals with constipation, bloating, feeling hungry an hour after eating, stubborn weight, or low energy, a total lack of fiber could easily be a contributing factor.
Fiber and Fat Loss
If you are working on leaning out, fiber might be the most underrated tool in your corner. High-fiber foods take longer to digest, keeping you full for a much longer stretch after a meal. That’s a huge win when you are in a calorie deficit and fighting off hunger between meals or before bed.
Soluble fiber forms a thick gel in your gut that slows down how fast food empties from your stomach. This means a gradual rise in blood sugar, a smaller insulin spike, and a wider window before hunger signals kick back in. When you are not constantly white-knuckling through hunger cravings, staying consistent with your nutrition becomes a whole lot easier. This can be especially helpful for our members who are in a fat loss phase.
High-fiber foods also have massive physical volume relative to their calorie count. A cup of raspberries, a big bowl of roasted broccoli, or a serving of lentils will fill you up without eating into your daily calorie budget. Over time, that combination of fullness and nutrient density makes a massive difference in body composition.
Not All Fiber Is the Same
This is where it gets interesting, and where most generic health advice falls short. There are two main types of fiber.
Soluble Fiber: This type dissolves in water to form a gel-like substance in your gut, slowing down digestion so it takes longer to absorb sugar, helping to stabilize blood sugar. These fibers also bind up fatty acids and help lower bad LDL cholesterol. Foods rich in soluble fiber include oats, apples, blueberries, peas, beans, and chia seeds.
Insoluble Fiber: This does not dissolve in water. Instead, it adds bulk to your stool and speeds up transit time through your digestive tract to prevent constipation. You will find it in whole wheat, the skin of fruit, prunes, brown rice, broccoli, cauliflower, nuts and seeds, and potatoes.
You can load up on several types of vegetables that contain both soluble and insoluble fiber, such as broccoli, brussels sprouts, carrots, artichoke, sweet potatoes, cabbage, and beets.
Prebiotic Fiber — Food For Your Gut Bacteria
This is the actual food your gut bacteria eat. When your microbiome ferments prebiotic fiber in the large intestine, it produces short-chain fatty acids like butyrate. Butyrate is the primary fuel for the cells lining your colon. It maintains the tight junctions that keep your gut barrier intact (ever heard the term “leaky gut”?), and supports the immune cells that distinguish between friend and foe. A balanced immune response means your body handles inflammation significantly better.
It’s worth knowing that polyphenols, the compounds that give colorful plant foods their pigment, also act as fuel for beneficial bacteria in a similar way to prebiotic fiber. Berries, dark chocolate, green tea, extra virgin olive oil, and deeply colored fruits and vegetables are among the richest sources. Eating a wide variety of colorful plants gives your microbiome more to work with across the board.
Common types of prebiotic fiber include:
- Inulin/FOS (fructooligosaccharides) – a natural plant-based compound that selectively feeds beneficial bacteria like Bifidobacterium. Found in garlic, onions, leeks, asparagus, Jerusalem artichokes, dandelion greens, and chicory root. Start with small amounts as it can cause gas until your gut adjusts.
- Pectin – a soluble fiber that ferments in the colon and feeds a broad range of beneficial bacteria. Found in apples, citrus fruits, berries, and carrots.
- Beta-glucan – a well-researched prebiotic fiber that also helps lower LDL cholesterol and stabilize blood sugar. Found in oats and barley.
- PHGG (SunFiber) – partially hydrolyzed guar gum, available as a supplement. Ferments slowly and is well tolerated by those with SIBO or IBS.
Resistant starch functions similarly to prebiotic fiber but is its own category. It skips digestion in the small intestine entirely and travels to the lower colon, where it feeds bacteria and produces butyrate. It’s one of the most effective ways to fuel the distal colon, the area where disease risk is highest. Cooking and then cooling foods like rice and potatoes increases their resistant starch content significantly. Found naturally in green bananas, lentils, legumes, and cooled cooked rice or potatoes.
Foods naturally high in prebiotic fiber and resistant starch:
- Garlic
- Onions and leeks
- Asparagus
- Jerusalem artichokes (one of the highest sources available)
- Chicory root
- Dandelion greens
- Apples (with skin)
- Oats and barley
- Lentils and chickpeas
- Flaxseeds
- Pistachios and cashews
- Green (underripe) bananas
- Cooked and cooled rice or potatoes
- Jicama
- Cocoa (unsweetened)
Why You Should Rotate Your Fiber Sources
Different fibers feed different parts of your gut and different strains of bacteria. Think of it as a race against time. Rapidly fermenting fibers like inulin and FOS get broken down early, in the first stretch of your large intestine. That’s great for the bacteria living there, but it means less fuel reaches the far end of the colon.
When the distal colon runs low on fermentable fiber, bacteria there start breaking down the gut’s own mucus lining instead. That shift drives up inflammation and is associated with higher rates of colorectal cancer and inflammatory bowel disease. This is exactly where slower-fermenting fibers like resistant starch (RS) are important. RS is found in green bananas, legumes, and cooked and cooled rice or potatoes. It acts more like a time-release capsule. It survives the early stretch and travels all the way to the far end of the colon, feeding the bacteria in the areas where disease risk is highest.
Eating the same fiber sources every day creates a narrow environment for your gut microbiome. Diversity in what you eat supports diversity in your gut bacteria, and a more diverse microbiome is associated with better metabolic health and a stronger immune response. Try rotating your vegetables throughout the week, cycling between different vegetables and legumes, as well as mixing up your grains rather than leaning on the same two or three foods every day.
Eating a wide variety of colorful plant foods also delivers polyphenols, plant compounds that feed beneficial bacteria and have well-documented anti-inflammatory effects. Berries are one of the richest polyphenol food sources you can eat!
3 Practical Ways to Get More Fiber
Upgrade What You Are Already Eating
You do not need to completely overhaul your kitchen. Start with simple swaps. Choose brown rice or quinoa over white rice. Keep the skin on your apples, pears, potatoes, and carrots, because that is where a massive chunk of the fiber and antioxidants live. Skip the fruit juice and eat the whole fruit instead to get the full benefit of the fruit, plus less sugar impact.
Rethink Your Snacks
Chips and crackers are some of the lowest-fiber items. Swapping them for fruit, raw vegetables with hummus, or a handful of nuts is the fastest way to hit your daily targets without changing your main meals. It’s also a simple way to cut out mindless snack calories while feeling completely satisfied.
Add Legumes to Your Weekly Rotation
Beans and lentils are among the most fiber-dense foods available, packed with both soluble and prebiotic fiber. Adding just one or two legume-based meals a week (like a lentil soup, a black bean taco night, or tossing chickpeas onto your daily salad) makes a massive dent in your weekly totals. Now you can even get bean-based pasta, which is loaded with both fiber and protein. Check out Bonza chickpea pasta and Veggie Craft peas, lentils, and cauliflower varieties that actually taste great!
Fiber Supplements and Easy Fiber Add-Ins
Ideally, you should try to get as much fiber from real foods, since it delivers a matrix of vitamins, minerals, and polyphenols that a powder in a tub simply cannot replicate. That said, if you are consistently tracking your intake and still falling short of your daily targets, using a supplement to close the gap is a perfectly smart move.
Supplements: If you go this route, you have a few options depending on how your gut handles things:
- Psyllium Husk: The gold standard and most thoroughly researched option available. Incredibly effective at stabilizing things, meaning it helps with both constipation and loose stools. It also carries the added benefit of helping lower LDL cholesterol.
- Guar Gum PHGG (SunFiber): Partially hydrolyzed guar gum is a great choice for sensitive systems that can’t tolerate other high-fiber supplements. It dissolves completely into water with zero taste or gritty texture. Because it ferments slowly, it is one of the best options if you deal with IBS or SIBO.
- Acacia Fiber: Similar to PHGG, acacia is gentle and slow-fermenting, making it another solid option if standard fibers tend to cause you grief.
- Inulin: A strong prebiotic that selectively feeds Bifidobacterium, the good bacteria in your gut. It works well for people with healthy digestion, but can cause significant bloating if you add too much too fast. Start low and slow.
Two Whole Foods Worth Calling Out
These aren’t supplements, but they function like one in terms of how easy they are to add to what you’re already eating:
- Chia seeds: 8 to 10 grams of soluble, gel-forming fiber per two tablespoons, plus omega-3 fatty acids. They absorb water and expand in your gut, slowing digestion and extending fullness. Stir into protein smoothies, oatmeal, or yogurt.
- Ground flaxseed: About 6 grams of fiber per two tablespoons, both soluble and insoluble, plus lignans, plant compounds with antioxidant and hormone-balancing properties. Ground absorbs significantly better than whole seed. Add to smoothies, oatmeal, salads as a topper, or baked goods.
A Few Tips When Adding More Fiber
Increase slowly. Adding a large amount of fiber all at once is a recipe for bloating, gas, and constipation. Add 2 to 3 grams per day and give your gut bacteria time to adjust. Then gradually add more over time.
Drink more water. Fiber absorbs water, and without enough of it, things can actually get worse instead of better. A good baseline is half your body weight in ounces of water per day, and be especially consistent about hydration when you’re increasing your fiber intake. This is especially important if you are taking a fiber supplement like psyllium husk, follow it up by drinking roughly 16oz of water directly after.
Fiber Content by Food Group
All values are based on USDA data. Because cooking styles and serving sizes change the actual fiber content, specific details are noted below.
Vegetables
- Green peas (cooked): 9g per cup (Soluble + Insoluble)
- Acorn squash (baked): 9g per cup (Soluble + Insoluble)
- Butternut squash (baked): 7g per cup (Soluble + Insoluble)
- Artichoke (raw): 7g per medium (Prebiotic inulin)
- Pumpkin (cooked): 7g per cup (Soluble pectin + Insoluble)
- Sweet potato (mashed, cooked): 6g per cup (Soluble + Insoluble)
- Broccoli (cooked): 5g per cup (Insoluble + Prebiotic)
- Carrots (cooked): 5g per cup (Soluble pectin)
- Asparagus (cooked): 4g per cup (Prebiotic inulin)
- Brussels sprouts (cooked): 4g per cup (Insoluble + Prebiotic)
- Spinach (cooked): 4g per cup (Insoluble)
- Sweet potato (baked): 4g per medium (Soluble + Insoluble)
- Potato (russet, baked with skin): 4g per medium (Insoluble + Resistant Starch)
- Corn (cooked): 3g per cup (Insoluble)
- Cauliflower (raw or cooked): 2g per cup (Insoluble)
- Cabbage (raw): 2g per cup (Insoluble)
- Onion (raw): 2g per medium (Prebiotic inulin/FOS)
- Garlic (raw): 1g per 3 cloves (Prebiotic inulin/FOS)
Fruits
- Raspberries (raw): 8g per cup (Insoluble + Soluble pectin)
- Blackberries (raw): 8g per cup (Insoluble + Soluble pectin)
- Avocado: 5g per half medium (Soluble + Insoluble)
- Pear (raw, with skin): 5g per medium (Soluble pectin + Insoluble)
- Kiwi (raw): 4-5g per 2 large (Soluble gel-forming)
- Apple (raw, with skin): 4g per medium (Soluble pectin + Insoluble)
- Blueberries (raw): 4g per cup (Soluble pectin)
- Orange (raw): 4g per large (Soluble pectin)
- Banana (slightly underripe): 3g per medium (Resistant Starch + Soluble)
- Strawberries (raw): 3g per cup sliced (Soluble pectin)
- Prunes: 2g per 3 whole (Insoluble + Soluble; high in sorbitol, skip if FODMAP-sensitive)
Whole Grains
- Barley (cooked): 6g per cup (Soluble beta-glucan)
- Oatmeal (cooked): 4g per cup (Soluble beta-glucan)
- Quinoa (cooked): 5g per cup (Insoluble)
- Brown rice (cooked): 4g per cup (Insoluble)
- Air-popped popcorn: 3.5g per 3 cups (Insoluble)
- Whole grain couscous (cooked): 2g per cup (Insoluble)
- Rice (cooked, then fully cooled): Varies based on cooling time (Resistant Starch)
Note: Cooling cooked rice converts a portion of digestible starch into resistant starch, increasing its gut benefits. This cook and cool method also goes for potatoes as well. As a bonus, the resistant starch remains present when reheated.
Beans and Legumes (all values cooked and drained)
- Navy beans: 9.6g per half cup (Soluble + Insoluble + Resistant Starch)
- Split peas: 8g per half cup (Soluble + Insoluble)
- Lentils: 7.8g per half cup (Insoluble + Some Prebiotic)
- Black beans: 7.5g per half cup (Soluble + Insoluble + Resistant Starch)
- Chickpeas: 6.2g per half cup (Insoluble + Some Prebiotic)
- Kidney beans: 5.7g per half cup (Soluble + Insoluble)
- Edamame (shelled): 4g per half cup (Soluble + Insoluble)
Nuts and Seeds
- Chia seeds: 8-10g per 2 tbsp (Soluble gel-forming)
- Flaxseed (ground): 6g per 2 tbsp (Soluble + Insoluble)
- Pumpkin seeds (whole, raw): 5g per 1 oz (Insoluble)
- Almonds (raw): 3.5g per 1 oz / ~23 almonds (Insoluble)
- Pistachios (raw): 3g per 1 oz / ~49 kernels (Insoluble + Prebiotic)
- Sunflower seeds (raw): 3g per 1 oz (Insoluble)
At the end of the day, fiber is not just about staying regular. It is one of the most thoroughly researched factors tied directly to long-term metabolic health, body composition, gut integrity, immune balance, and chronic disease prevention. Most people are not getting enough, and the ones who are usually miss out on variety.
Start exactly where you are today. Add a little bit more each week, rotate your sources, and keep up with your water intake. Your gut will handle the rest!
