Fiber-maxxing is a social media trend based on eating more dietary fiber. While there’s no uniform outcome or definition for this trend, it is oriented around increasing daily fiber intake as much as possible. Let’s talk more about fiber and this trend.
What is fiber?
Fiber is a non-digestible complex carbohydrate found in foods of plant origin; think fruits, vegetables, grains, legumes, nuts, and seeds. Foods of animal origin – meat, seafood, poultry, dairy, eggs – do not contain fiber. Fiber is categorized into two main types:
- Soluble fiber dissolves in water. It is fermented in the colon, creating short chain fatty acids that support a healthy gut microbiome. It also draws water into the digestive tract, preventing stools from becoming too dry.
- Foods high in soluble fiber include oats, beans, berries, and apples.
- Insoluble fiber does not dissolve in water. Its role is adding bulk to the stool, making stool easier to pass.
- Foods high in insoluble fiber include whole grains, nuts, and seeds.
Most plant foods contain a mixture of soluble and insoluble fiber; these fibers are considered intact and intrinsic in their food source. In addition to these fibers that are inherent in plant foods, the US Food and Drug Administration (FDA) has also identified seven isolated, non-digestible compounds that meet the definition of dietary fiber. These include beta-glucan soluble fiber, psyllium husk, cellulose, guar gum, pectin, locust bean gum, and hydroxypropylmethylcellulose. These isolated compounds are added as food ingredients to increase dietary fiber and confer similar health benefits as soluble and insoluble fiber. They will be included on the ingredient list when added to a food product and are often added to bars, cereals, alternative pastas, yogurt, packaged baked goods, and products marketed as being low-carb or high fiber.
Because fiber is not fully digestible, it contributes fewer calories than other carbohydrates. Carbohydrates contribute four calories per gram, whereas fiber contributes 1.5-2.5 calories per gram.
The FDA requires that dietary fiber is listed on the Nutrition Facts panel. It is nested beneath Total Carbohydrate. Soluble and insoluble fiber must be listed on the Nutrition Facts panel if the manufacturer makes any claims on the packaging about the health benefits of fiber or the amount contained in the product. Otherwise, it’s optional to include the amount of soluble and insoluble fiber in the product ,so you will not always see it listed there.
The Daily Value for fiber is 28g.
Health benefits of fiber
Fiber has a variety of health benefits so it’s no surprise that it’s finally gone viral. Dietary fiber promotes digestion, glycemic control, heart health, and reduces risk for colorectal cancer. Physiological benefits of fiber include:
- lower post-meal blood glucose and insulin levels
- lower fasting low density lipoprotein (LDL) cholesterol or fasting blood glucose
- lower blood pressure
- increased frequency of bowel movements
- improved mineral absorption in the gastrointestinal tract
- reduced energy intake
How much fiber do I need?
The Adequate Intake (AI) for fiber is 14g per 1000 calories. Adequate Intakes are the amount that will cover the needs of the majority of people when there is not enough evidence to calculate a Recommended Dietary Allowance. The AI for fiber is based the mean amount of fiber required to achieve cardiovascular health benefits. Consuming 14g per 1000 calories translates to about 25g per day for women and 38g per day for men. Mean intake of fiber in the US is only about 17g per day, indicating that we have plenty of room for improvement when it comes to dietary fiber.
American Institute for Cancer Research recommends getting at least 30g per day of fiber to reduce colorectal cancer risk.
Is there such thing as too much fiber?
While people may experience gastrointestinal symptoms like bloating or gas when increasing fiber intake, high intake of dietary fiber in healthy individuals does not have any adverse health effects. Fiber intake also tends to be self limiting since most high fiber foods are less energy dense and contribute to increased satiety. Added fibers used as food ingredients, like those mentioned above, are more likely to cause symptoms like gas, bloating, diarrhea, or constipation compared to fiber that is naturally occurring in food. People with certain medical conditions, like IBS, may need to pay particular attention to the types and quantities of fiber that they consume. It’s a good idea to slowly increase the types of high fiber foods you are eating so that you can understand if a particular food is causing any symptoms and speak with your healthcare provider if you have any concerns.
Best sources of fiber
The Dietary Guidelines for Americans emphasize obtaining nutrients from food sources rather than supplements whenever possible. The FDA regulates nutrient content claims for fiber, which include:
- Excellent source: contains 20% or more of the Daily Value (5.6g or more per serving)
- Good source: contains 10-19% of the Daily Value (2.8-5.3g per serving)
| Food | Serving size | Dietary fiber (grams) |
| Avocado | 1 cup | 5g |
| Blueberries | 1 cup | 6.2g |
| Broccoli | 1 cup, cooked | 5.2g |
| Chia seeds | 1 tablespoon | 4.1g |
| Flax seeds | 1 tablespoon | 2.8g |
| Kiwi | 1 cup | 5.4g |
| Lentils | 1/2 cup (cooked) | 7.8g |
| Oats | 1/2 cup (dry) | 8.25g |
| Popcorn | 3 cups (popped) | 5.8g |
| Pumpkin seeds | 1 ounce | 5.2g |
| Raspberries | 1 cup | 9g |
| Spinach | 1 cup (cooked) | 4.3g |
| Split peas | 1/2 cup (cooked) | 8.2g |
| Tortillas, whole wheat | 1 ounce | 2.8g |
Ways to increase fiber intake
When increasing fiber intake, add higher fiber foods gradually and be sure to drink enough water. Increasing fiber intake without hydrating can lead to constipation and gastrointestinal distress. Some simple ways to increase your fiber intake include:
- Add 1/2 cup fresh or frozen berries to oatmeal or cold cereal
- Mix 1-2 tablespoons chia or ground flax seed into yogurt
- Add two handfuls of spinach to a smoothie
- Top salad with pumpkin seeds or chopped nuts
- Add spiralized zucchini or roasted vegetables to whole grain pasta
- Include fruits and nuts in your daily snacks
- Choose foods with whole grain listed as the first ingredient
Take home message
While fibermaxxing may sound extreme, most Americans aren’t currently consuming enough dietary fiber to achieve its many health benefits. Increasing dietary fiber is likely to be a good thing when it comes to satiety, gastrointestinal health, cardiovascular health, and colorectal cancer risk. Choose minimally processed foods that are naturally high in soluble and insoluble fiber.