Dietary Fiber: A Crucial Nutrient For Metabolic Health

Why fiber is a key nutrient for metabolic health – and how to make sure you're getting enough of it.

woman walking down a suburban sidewalk with a tote bag and basket of produce

If there's a single nutrient to consume for metabolic health, it's fiber.

Why? Fiber is unique in its ability to support all aspects of metabolic health. Metabolic health measures whether our bodies can effectively process and use the foods we eat. 

When we have metabolic health, our bodies can convert the food we eat into energy, repair cells, and eliminate toxins efficiently. It considers factors like blood sugar levels, insulin sensitivity, and cholesterol levels. 

Here's why fiber is so essential for metabolic health and how you can make sure you're getting enough.

Dietary Fiber 101

A quick background on fiber: it's a carbohydrate that passes mostly undigested through your G.I. tract.

Fiber comes from plants and is found in two forms: insoluble and soluble fiber.1 Soluble fiber dissolves in water to form a gel-like substance and is fermented by your gut bacteria (more on why this is important below). It's found in foods like oats, beans, and apples and helps slow digestion and keep you feeling full after eating.

Insoluble fiber (sometimes called roughage) doesn't dissolve in water, so it doesn't form a gel. It keeps things moving in your gut and is found in foods like wheat bran, vegetables, and whole grains. Both types of fiber have health benefits, and most foods have a mix of both.1

Dietary Fiber and Metabolic Health

As mentioned earlier, metabolic health tells you how well your body can process and use the foods you eat. When the body can't process food effectively, it can lead to a whole host of problems like insulin resistance, high blood glucose levels, weight gain, and eventually metabolic syndrome.

<p class="pro-tip"><strong>Learn more about </strong> <a href="/blog/insulin-resistance-vs-prediabetes">insulin resistance vs prediabetes</a>.</p>

Metabolic syndrome is a condition characterized by:2

  • Insulin resistance
  • High blood sugar levels
  • High triglyceride levels
  • Low HDL (good) cholesterol levels
  • Abdominal obesity

So where does fiber fit in? 

Fiber reduces the risk of metabolic syndrome by helping improve insulin sensitivity, blood sugar control, and cholesterol levels. 3

<p class="pro-tip"><strong>Learn more about </strong> <a href="/blog/benefits-stable-glucose">the benefits of stable blood sugar</a>.</p>

Let's look more closely at fiber and all the ways it helps.

Metabolism, Fiber, and Weight

If metabolic health is the efficient conversion of food to energy, fiber is a crucial nutrient. Fiber slows down digestion and helps you feel full longer.4 High fiber diets are linked to a healthy weight, possibly due to their effect on hormones that help you feel fuller and eat less.1, 5

Eating more fiber is also linked to reduced abdominal obesity. Abdominal obesity, or visceral fat, is considered especially problematic and is related to an increased risk of insulin resistance, diabetes, and heart disease. 

In one study, each 10 gram increase in soluble fiber intake reduced the rate of abdominal obesity by almost 4 percent.6

<p class="pro-tip"><strong>Learn how to </strong> <a href="/blog/lower-belly-fat">get rid of lower belly fat</a>.</p>

a bowl of bean salad garnished with parsley
Foods rich in soluble fiber, like beans, promote a healthy gut flora.

Fiber is a Powerful Nutrient for Gut Health

Fiber provides food for the beneficial bacteria that live in the intestine (your microbiome). Microbiome diversity is critical for gut health, and fiber is a major factor in microbiome composition.7

Prebiotic fiber, in particular, has been shown to improve gut health by promoting the growth of beneficial bacteria and inhibiting the growth of harmful bacteria.8

Your gut microbes also play a significant role in your metabolic health. A healthy gut microbiome is linked to a reduced risk of obesity, insulin resistance, and chronic inflammation, all of which are risk factors for metabolic syndrome.9

Microbes keep digestion and the gut environment healthy and happy while reducing inflammation and protecting the gut lining. Beneficial gut bacteria ferment dietary fiber and produce short-chain fatty acids (SCFAs) like butyrate, acetate, and propionate. 

Butyrate has been shown to protect against colon cancer and is also an essential energy source for the cells lining the intestine.10

Short-chain fatty acids are involved in everything from inflammation regulation to insulin sensitivity.11

A diet high in fiber can promote the growth of beneficial bacteria and increase SCFA production. This, in turn, can improve gut health, reduce inflammation, and support metabolic health.

<p class="pro-tip"><strong>Learn more about </strong> <a href="/blog/prebiotic-foods-list">the best prebiotic foods for gut health</a>.</p>

Fiber Intake Influences Blood Glucose and Insulin 

Fiber can help keep blood sugar levels in check by slowing the absorption of sugar from the intestine. This is not only helpful for people with diabetes or prediabetes but for anyone interested in keeping blood sugar stable.

A diet high in fiber has been linked with improved blood sugar control and a lower risk of type 2 diabetes.12 One study found that people who ate more fiber had a 33 percent lower risk of diabetes than those with a low fiber intake.13

Fiber can also help lower insulin levels. Insulin is a hormone that helps the body store and use sugar from the blood. When insulin levels are too high, it can lead to weight gain and other health problems. One study found that high soluble fiber intake increased insulin sensitivity after only three days.14

There are likely multiple mechanisms at play, but one reason fiber can help with blood sugar is that, unlike other carbohydrates that can raise blood sugar, fiber is not broken down and absorbed into the bloodstream in the same way. Most fiber-rich foods are low on the glycemic index, so they don't cause the same spikes in blood sugar.

If you want to experiment to see how your blood sugar responds to fiber, a continuous glucose monitor paired with the Signos app gives you real-time, valuable insights.

Fiber Provides Cardiovascular Protection

Fiber is also linked to lower cardiovascular disease, inflammation, and blood pressure risk.15 Fiber provides powerful protection against cardiovascular disease. One study suggests that even a 10 gram fiber increase reduces mortality risk from heart disease by 14 percent.16

Why is it so good for your heart health? Fiber can lower cholesterol levels by binding to cholesterol in the intestine and preventing its absorption.17This is especially true for soluble fiber. 

Short-chain fatty acids also play a role in heart health. Animal studies suggest that propionate can help lower cholesterol production in the body and reduce the formation of plaque that contributes to heart disease.18

Inflammation is especially damaging to the cardiovascular system. Not only does fiber help reduce inflammation via short-chain fatty acids in the gut, but it may also decrease inflammatory signaling molecules that adversely affect health and are linked to heart disease. 1

a dish of shaved Brussels sprouts with slivered almonds
Brussels sprouts are a good source of fiber, vitamin C, and vitamin K.

How Much Fiber Do You Need for Metabolic Health?

The amount of fiber you need to eat depends on your age and sex. The Recommended Dietary Allowance (RDA) for fiber is 14 grams of fiber for every 1000 calories.19

For most adults, this translates to 25 to 35 grams of fiber a day (assuming an 1800 to 2200 calorie diet). 

Why Don't People Eat Enough Fiber?

The average American only consumes about 17 grams of fiber daily, with only about 5 percent of the population meeting adequate intake.20

There are a few potential reasons for this:

  • Many people don't know how much fiber they need or what foods contain fiber.
  • Intake of fresh fruits, vegetables, whole grains, legumes, and nuts, is low for many people.
  • Processed foods are often low in fiber.
  • The Western diet is typically high in calories and fat and low in fiber.

<p class="pro-tip"><strong>Read about </strong> <a href="/blog/ultra-processed-foods">how ultra-processed foods affect blood sugar</a>.</p>

What Foods Are High in Fiber?

The best way to get more fiber is to experiment with high-fiber foods. Luckily, there are many delicious high-fiber foods you can add to your diet:

  • Fruits, especially berries, avocados, and apples
  • Vegetables, especially leafy greens, Brussels sprouts, and broccoli
  • Whole grains, such as oats, quinoa, and brown rice 
  • Legumes, such as black beans, lentils, and chickpeas
  • Nuts and seeds, especially chia and flax

Fiber supplements like psyllium or acacia can also be an option. Just make sure they don't have added sugar or artificial flavoring.

How to Increase Fiber in Your Diet for Metabolic Health

Even if you know what foods are high in fiber, it can be tough to increase your intake if you're not used to eating a lot of fiber-rich foods. Here are a few tips to help you get started:

  • Start slowly: If you're not used to eating a lot of fiber, gradually increase your intake over a few weeks. This will help your body adjust and avoid side effects like gas or bloating.
  • Drink plenty of water: Drinking enough water is key to avoiding constipation while increasing your fiber intake (yes, too much fiber without water can actually make you constipated). Aim for eight glasses of water per day.
  • Swap refined for whole grains: Whole grains are a great source of fiber, so try swapping refined grains like white bread and pasta for whole grain options. Even better? Try legume-based pasta like lentil or garbanzo for extra fiber and protein.
  • Include vegetables at every meal: Vegetables are packed with fiber, so make sure to have them at every meal. Salads, roasted veggies, and vegetable soup are all easy ways to get more fiber.

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/low-glycemic-vegetables">high-fiber, low-glycemic vegetables</a>.</p>

woman in workout clothes drinking water from a reusable bottle
Make sure that your high-fiber diet includes plenty of water as well.

Are There Any Side Effects from Eating More Fiber?

If you're not used to eating a lot of fiber, you may experience side effects like bloating, gas, and abdominal pain. This is temporary and related to the changes in your gut flora, a good thing! But it can be uncomfortable.

To avoid these side effects, start slowly and increase your intake gradually. This will give your body time to adjust. Drinking plenty of water is also essential because fiber absorbs water and can lead to constipation if you don't drink enough.

<p class="pro-tip"><strong>Read about </strong> <a href="/blog/water-lower-blood-sugar">hydration and blood sugar</a>.</p>

If you have any digestive issues like irritable bowel syndrome, small intestinal bacterial overgrowth, or irritable bowel disease, it may not be recommended to suddenly bump up your fiber intake, as this can make symptoms worse. However, you may still be able to increase your fiber intake slowly and with the guidance of a healthcare professional.

Final Thoughts on Fiber for Metabolic Health

Metabolic health isn't about a fad diet or quick fix. It's about making long-term changes to your lifestyle and diet that will improve your health in the long run.

No single food will magically improve your health, but fiber comes close. Fiber is a nutritional powerhouse and increasing your intake can profoundly affect your metabolic health.

It's a simple change you can make today that can have a long-lasting impact.

<p class="pro-tip"><strong>Learn more about </strong> <a href="/blog/macronutrients">mastering your macros: carbs, protein & fat</a>.</p>

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References

  1. Lattimer, J. M., & Haub, M. D. (2010). Effects of dietary fiber and its components on metabolic health. Nutrients, 2(12), 1266–1289. https://doi.org/10.3390/nu2121266
  2. “Metabolic Syndrome - What Is Metabolic Syndrome? | NHLBI, NIH.” Accessed July 22, 2022. https://www.nhlbi.nih.gov/health/metabolic-syndrome.
  3. Chen, J. P., Chen, G. C., Wang, X. P., Qin, L., & Bai, Y. (2017). Dietary Fiber and Metabolic Syndrome: A Meta-Analysis and Review of Related Mechanisms. Nutrients, 10(1), 24. https://doi.org/10.3390/nu10010024 
  4. Howarth, N. C., Saltzman, E., & Roberts, S. B. (2001). Dietary fiber and weight regulation. Nutrition reviews, 59(5), 129–139. https://doi.org/10.1111/j.1753-4887.2001.tb07001.x 
  5. Tucker, L. A., & Thomas, K. S. (2009). Increasing total fiber intake reduces risk of weight and fat gains in women. The Journal of nutrition, 139(3), 576–581. https://doi.org/10.3945/jn.108.096685 
  6. Hairston, K. G., Vitolins, M. Z., Norris, J. M., Anderson, A. M., Hanley, A. J., & Wagenknecht, L. E. (2012). Lifestyle factors and 5-year abdominal fat accumulation in a minority cohort: the IRAS Family Study. Obesity (Silver Spring, Md.), 20(2), 421–427. https://doi.org/10.1038/oby.2011.171 
  7. Cronin, P., Joyce, S. A., O'Toole, P. W., & O'Connor, E. M. (2021). Dietary Fibre Modulates the Gut Microbiota. Nutrients, 13(5), 1655. https://doi.org/10.3390/nu13051655 
  8. Holscher H. D. (2017). Dietary fiber and prebiotics and the gastrointestinal microbiota. Gut microbes, 8(2), 172–184. https://doi.org/10.1080/19490976.2017.1290756 
  9. Dabke, K., Hendrick, G., & Devkota, S. (2019). The gut microbiome and metabolic syndrome. The Journal of clinical investigation, 129(10), 4050–4057. https://doi.org/10.1172/JCI129194 
  10. Tan, J., McKenzie, C., Potamitis, M., Thorburn, A. N., Mackay, C. R., & Macia, L. (2014). The role of short-chain fatty acids in health and disease. Advances in immunology, 121, 91–119. https://doi.org/10.1016/B978-0-12-800100-4.00003-9 
  11. Myhrstad, M., Tunsjø, H., Charnock, C., & Telle-Hansen, V. H. (2020). Dietary Fiber, Gut Microbiota, and Metabolic Regulation-Current Status in Human Randomized Trials. Nutrients, 12(3), 859. https://doi.org/10.3390/nu12030859 
  12. Meyer, K. A., Kushi, L. H., Jacobs, D. R., Jr, Slavin, J., Sellers, T. A., & Folsom, A. R. (2000). Carbohydrates, dietary fiber, and incident type 2 diabetes in older women. The American journal of clinical nutrition, 71(4), 921–930. https://doi.org/10.1093/ajcn/71.4.921 
  13. Schulze, M. B., Schulz, M., Heidemann, C., Schienkiewitz, A., Hoffmann, K., & Boeing, H. (2007). Fiber and magnesium intake and incidence of type 2 diabetes: a prospective study and meta-analysis. Archives of internal medicine, 167(9), 956–965. https://doi.org/10.1001/archinte.167.9.956 
  14. Weickert, M. O., Möhlig, M., Schöfl, C., Arafat, A. M., Otto, B., Viehoff, H., Koebnick, C., Kohl, A., Spranger, J., & Pfeiffer, A. F. (2006). Cereal fiber improves whole-body insulin sensitivity in overweight and obese women. Diabetes care, 29(4), 775–780. https://doi.org/10.2337/diacare.29.04.06.dc05-2374 
  15. Streppel, M. T., Ocké, M. C., Boshuizen, H. C., Kok, F. J., & Kromhout, D. (2008). Dietary fiber intake in relation to coronary heart disease and all-cause mortality over 40 y: the Zutphen Study. The American journal of clinical nutrition, 88(4), 1119–1125. https://doi.org/10.1093/ajcn/88.4.1119 
  16. Pereira, M. A., O'Reilly, E., Augustsson, K., Fraser, G. E., Goldbourt, U., Heitmann, B. L., Hallmans, G., Knekt, P., Liu, S., Pietinen, P., Spiegelman, D., Stevens, J., Virtamo, J., Willett, W. C., & Ascherio, A. (2004). Dietary fiber and risk of coronary heart disease: a pooled analysis of cohort studies. Archives of internal medicine, 164(4), 370–376. https://doi.org/10.1001/archinte.164.4.370 
  17. Soliman G. A. (2019). Dietary Fiber, Atherosclerosis, and Cardiovascular Disease. Nutrients, 11(5), 1155. https://doi.org/10.3390/nu11051155 
  18. Haghikia, A., Zimmermann, F., Schumann, P., Jasina, A., Roessler, J., Schmidt, D., Heinze, P., Kaisler, J., Nageswaran, V., Aigner, A., Ceglarek, U., Cineus, R., Hegazy, A. N., van der Vorst, E., Döring, Y., Strauch, C. M., Nemet, I., Tremaroli, V., Dwibedi, C., Kränkel, N., … Landmesser, U. (2022). Propionate attenuates atherosclerosis by immune-dependent regulation of intestinal cholesterol metabolism. European heart journal, 43(6), 518–533. https://doi.org/10.1093/eurheartj/ehab644 
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About the Author

Caitlin Beale Headshot
Caitlin Beale is a registered dietitian and nutrition writer with a master’s degree in nutrition. She has a background in acute care, integrative wellness, and clinical nutrition.
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