Why is fiber important for total health and weight loss?

Melanie Basel, RDN

For those on a weight loss or health journey, calories and macronutrients like protein, fat, and carbohydrates are often the primary focus, but what about fiber? The USDA recommends a daily amount of fiber of 25 grams for women and 38 grams for men, yet the average American adult consumes only 10-15 grams of fiber per day. 

Here, we will discuss the health benefits of fiber, how fiber relates to weight loss, and how to incorporate more into your day. 

What are the different types of fiber?

Fiber is a type of carbohydrate that the body cannot digest. The two main types of fiber are soluble fiber and insoluble fiber. 

  • Soluble fibers dissolve in water. They are viscous or fermentable fibers that slow the digestive process down by pulling water into the intestines and creating a gel-like substance. Fermentable fibers act as food for gut bacteria, which helps promote a healthy microbiome (more on this later). Not only does this gel-like substance help us feel fuller for longer periods of time, it also helps to reduce absorption of sugar and cholesterol in the body. 
  • Insoluble fibers do not dissolve in water. They are digested more quickly and provide bulk to stool. This type of fiber helps to promote regular bowel movements and prevent both constipation and diarrhea.

Foods high in fiber—like vegetables, fruits, nuts, seeds, beans, legumes, and whole grains—typically contain a combination of both soluble and insoluble fiber. Check out the charts at the end of this post for a comprehensive list of fibrous foods and their fiber content.

What are the health benefits of increasing dietary fiber?

Consuming the recommended amount of dietary fiber is associated with a reduced risk of various health conditions including:

  • Coronary artery disease
  • Stroke
  • Hypertension
  • Diabetes, and
  • Gastrointestinal disorders.

Increasing fiber intake has been shown to:

  • Improve  levels of cholesterol and triglycerides
  • Lower blood pressure
  • Improve blood sugar control
  • Promote weight loss, and 
  • Play a role in improving immune function.

Let’s take a deeper look into how fiber can help improve these health markers. 

How does fiber reduce vascular disease risk?

To understand the role fiber plays in reducing the risk of heart diseases and other vascular diseases like strokes or aneurysms it’s important to understand how these diseases develop over time. 

Hyperlipidemia is defined as an elevated level of lipids—like cholesterol and triglycerides—in the blood. Hyperlipidemia is a risk factor for developing vascular diseases as the accumulation of these lipids creates plaque buildup in the arteries, also known as atherosclerosis. 

In a blood test, lipids are broken down into total serum cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides. Research shows that elevated levels of LDL cholesterol (i.e. “bad” cholesterol) increase the risk of heart disease since this type of cholesterol can build up in the arteries. In contrast, HDL cholesterol (i.e., “good” cholesterol) is protective of heart health as it carries cholesterol back to the liver where it can be removed from the body.

Soluble or viscous fibers reduce total serum cholesterol and ”bad” cholesterol levels by interfering with bile acid production, a process that requires cholesterol. Soluble fiber binds to bile acids in the small intestine and excretes them from the body through the stool.

Due to the reduced amount of bile acids available, the liver will pull cholesterol from the blood to make new bile acids, thereby decreasing levels of cholesterol in the blood. Fermentable fibers also help reduce levels by producing types of fatty acids that inhibit the activity of an enzyme needed to make cholesterol, thus lowering cholesterol production. 

How does fiber help control blood sugar?

Dietary interventions are the most effective approach to controlling and preventing Type 2 Diabetes. Fiber is one of those interventions that can have a significant impact. Here’s how.

Dietary fibers form a viscous, gel-like substance in the small intestine which can decrease the how quickly the body breaks down carbohydrates into glucose. This leads to a lower glucose response after meals and, as a result, lower levels of insulin. 

Studies evaluating the effects of increasing dietary fiber by 10 grams per day in individuals with Type 2 Diabetes showed improvements in hemoglobin A1c—a marker that provides a 3-month average of blood sugar levels— as well as improvements in fasting blood sugar and insulin sensitivity. 

How does increasing fiber help to promote weight loss?

Increased fiber intake has been associated with improved markers of body weight, visceral adiposity (belly fat in your abdominal cavity that surrounds organs like the liver, kidneys, and intestines), insulin sensitivity, and inflammatory markers. Here’s how.

High-fiber foods are more satiating or filling than lower-fiber foods. In clinical trials that documented individuals’ food consumption, high-fiber meals resulted in decreased intake during that meal as well as the following meal. This is due to fibrous foods expanding in the stomach, creating the feeling of fullness. Moreover, many high-fiber foods like fruits and vegetables are high in volume and nutrients, but low in calories. Filling up your plate with these foods can increase the amount of food you eat without increasing the amount of calories you consume.

Another potential way fiber may impact weight loss is through the fermentation of dietary fibers. This process increases the diversity of the gut microbiome and the production of short-chain fatty acids, which have been shown to enhance the production of gut peptides like glucagon-like peptide-1 (GLP-1), sound familiar? 

What is the role of fiber in gut health?

There is emerging research on the importance of a healthy gut for, mental health, immunity, healthy weight, and disease prevention. The disruption of gut microbiota, referred to as dysbiosis, is associated with obesity, diabetes, bowel disease, and autoimmune diseases. 

Fiber plays a role in promoting a healthy gut microbiome, which may produce anti-inflammatory effects. Since chronic, low-grade inflammation is characteristic of many chronic diseases, fiber may help to reduce disease risk through its anti-inflammatory effects. There is increasing evidence that fermentable fibers (found in fruits, vegetables, beans, nuts, seeds, and whole grains) are associated with high levels of gut microbiome diversity and may positively influence the composition of the intestinal microbiota and aid in nutrient absorption as a result.

Fiber may also help prevent and improve gastrointestinal disorders like diverticular disease, hemorrhoids, and irritable bowel syndrome (IBS). Research has shown improvements in IBS symptoms among patients supplementing with certain fibers like psyllium husk.

Are there any adverse effects of increasing fiber intake?

The most commonly reported effect of increasing fiber intake is gastrointestinal discomfort like gas or bloating, diarrhea, and constipation. It is recommended to increase fiber intake gradually and to maintain adequate fluid intake and movement throughout the day to prevent these unwanted side effects. 

What about fiber supplements?

While we recommend getting the majority of fiber through whole food-based sources, fiber supplements can be a great adjunct to the diet to increase overall fiber intake and/or to address constipation. Psyllium husk powder is a good option for fiber supplements as it contains both soluble and insoluble fiber. It is recommended to start slow with 1 tsp per day and increase as needed to 2-3 tsp per day to supplement the diet. Fiber supplements may also interfere with the absorption of some medications if taken at the same time, so make sure to discuss with a healthcare professional prior to starting a fiber supplement. 

What is the recommended daily amount of fiber?

The USDA recommends a daily amount of fiber of 25 grams for women and 38 grams for men. On average, American adults are consuming 10-15 grams of total fiber per day. Here are a few tips on how to get there:

 High fiber foods include:

  • Vegetables
  • Fruit
  • Nuts 
  • Seeds
  • Beans 
  • Legumes 
  • Whole grains 

13 ways to add fiber to your diet

  1. Follow the balanced plate framework with ¼ plate protein, ¼ plate fiber-rich carbohydrates (like starchy vegetables, lentils, whole grains, beans, legumes or fruit) and ½ plate fruits and vegetables
  2. Add ground flaxseed to a protein smoothie 
  3. Sprinkle chia seed on Greek yogurt, in chia seed pudding, or in overnight oats
  4. Add beans or chickpeas to a salad 
  5. Cut up raw vegetables to dip in some hummus or tzatziki for a snack 
  6. Swap out white rice for a higher-fiber grain like quinoa 
  7. Choose higher-fiber fruits to snack on like berries, apples, or pears
  8. Swap out juices for whole fruits and vegetables (bonus points for keeping the skin on certain foods like apples or potatoes)
  9. Swap out regular pasta with chickpea pasta 
  10. Choose a whole wheat bread with at least 3g of fiber per serving
  11. Choose from any of these 20 easy ways to eat more vegetables
  12. Make your own trail mix with homemade popcorn, nuts, and dried fruit
  13. Add a fiber supplement like psyllium husk 

Melanie Basel, RDN

About the Author

Melanie is a Registered Dietitian with 8 years of experience in nutrition and is a Certified Lactation Counselor. She started her career as an RD in an inpatient hospital setting caring for patients in the ICU, but later found her love of nutrition coaching. She is so passionate about helping people live healthier, more fulfilled lives through personalized nutrition plans that are sustainable. In her spare time, Melanie loves cooking, hiking, weight lifting, and chasing after her toddler. She would love to help you reach your goals!

Scroll to see all categories

Join the Community

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

Popular Articles