Fiber is actually not a nutrient and it doesn’t provide the body with energy or calories. It’s also not digestible or absorbable by the body, but its health benefits earn it the designation of “phytonutrient.” Fitness professionals know that the “average American” (which includes many of our clients) likely isn’t taking in enough fiber.
But what is fiber? What are its benefits?
How much is enough? And how can fiber help clients meet health and weight goals? That’s a lot of questions! Here are some simple answers about this complex carbohydrate.
Fiber in a Nutshell—or an Apple Skin
Fiber is what gives plants their shape and structure, and it’s found only in plant foods, not animal-based ones. The shape and structure of fiber is what gives our body, most importantly our gastrointestinal tract, the bulk that provides many benefits. To reap the many benefits of fiber such as maintaining a healthy weight, satiety, glucose control, cholesterol reduction, cancer prevention, and gut health from prebiotics, boost your intake of plants.
America: Falling Short on Fiber
In 2014, the average American intake of fiber was only 16 grams per day. The recommended intake of fiber is 25–38 g per day (according to the NASM nutrition course). That’s a big disparity! Women should aim for 25 g of fiber per day, and men should target 38 g (or 21 g for women and 30 g for men daily for those over the age of 51).
Consuming more fruits, vegetables, whole grains, beans, legumes, nuts and seeds will increase fiber intake. The growing trend of increased plant-based intake (as in flexitarian diets—an expansion on the practice of Meatless Mondays) will hopefully increase the intake of fiber in the American population.
Whole Foods: The Best “Package” for Fiber
In spite of its many health benefits, fiber is not a cure-all that many seek from products, but it is a healthy focus when trying to improve overall health. In fact, it is one number I recommend paying attention to on the food label. I typically recommend paying more attention to reading the more important ingredients list, eating intuitively and eating more whole foods versus the numbers. When people focus on eating whole food versus looking at numbers, they are naturally more satisfied.
Over the years as refining and processing foods has become more prevalent, fiber has become less available in prepared products. This is even more of a reason to focus on whole, unprocessed foods. Take the apple-versus-applesauce-versus-apple-juice example:
- 1 medium apple with the peel contains 4.4 g of fiber; while
- 1/2 cup of applesauce contains 1.4 g of fiber; and
- 4 ounces of apple juice contains 0 g fiber!
Juicing—a popular trend—actually eliminates the fiber from the vegetables and fruits because juicers extract the fiber-filled pulp. And it’s not just fruits that contain more fiber when they’re not processed: The same holds true for soybeans versus tofu. A 1/2 cup serving of soybeans contains 5 g of fiber, whereas 1/2 cup of tofu only has 1 g of fiber.
It is recommended to receive your fiber intake from whole foods over fiber supplements or fortified foods. The foods that contain fiber also contain many other nutrients that a supplement may not contain. Research also shows that a fiber supplement may not have the same power of increasing satiety or managing blood sugar and cholesterol as the whole food does. Fiber-fortified foods may also cause more gastrointestinal issues.
There is not a box, powder or cleanse that you can purchase that will do for you what eating whole food can. Save your money on products and put it into real food. It’s the most beneficial way to reap the produce’s full nutrient and phytonutrient benefits.
Two Types of Fiber, Many Rewards
There are two kinds of fiber: soluble and insoluble. Both are beneficial and provide different perks. All plant foods contain a combination of both insoluble and soluble, but some have a higher amount of one over the other. Take the apple/applesauce/juice example again: The skin of the apple is a source of insoluble fiber, and the inside flesh contains soluble. The juice contains neither. Soluble fiber dissolves in water and insoluble fiber does not. Fiber’s solubility is what determines its benefits.
Insoluble fiber is cellulose, hemicellulose and lignin. Although insoluble fiber doesn’t dissolve in water, it does retain water and helps waste and toxins to move through our system more rapidly. Increasing plant intake usually allows us to feel better and have more energy as it helps the body naturally detoxify. Let your intestines, kidney, liver, and spleen work!
Insoluble fiber is found in foods such as cauliflower, green beans, and the skin of fruits. It helps with colon and breast cancer prevention, regularity and constipation prevention and diverticulosis. The indigestible parts of the plants are also prebiotics for our gut health to feed the probiotics.
Soluble fiber like glucan, psyllium, gum and pectin become gummy substances when water is added—for example, when chia seeds are put in liquid to make chia pudding. This gummy quality allows it to bind to cholesterol, helping the body excrete it. This is also how soluble fiber helps slow the rate at which blood glucose rises—it slows the absorption of the glucose into the bloodstream.
Foods such as oats, beans, apples, carrots and flax are sources of soluble fiber, and they help to promote satiety, a healthy weight, cholesterol reduction and blood glucose control.
Encouraging Clients to Boost Fiber Intake
Many people begin an exercise program for weight loss, then find that they have increased hunger. This is due to increased energy expenditure. One way to help keep hunger in check is increasing fiber intake. Not only does fiber contain zero calories, but the foods that are high fiber are also lower in calories and fat than many other foods.
Caution not to go overboard as there is too much of a good thing. Too much fiber may cause constipation and decrease nutrient absorption. Increase fiber intake gradually and also increase water intake to prevent constipation.
Tip: Fiber is not recommended right before a workout as it may increase gastrointestinal upset. Focus on adequate fiber intake in the meals and snacks post exercise or training.
Easy Ways to Fiber Up
A great place to start with increasing fiber intake is by using the plate method, which includes filling half your plate with vegetables and fruit at each meal. The plate method is a more realistic way to track portions for a healthy weight than measuring cups or counting calories. Another method is to aim for the recommended 5 servings (or more) of vegetables and fruits per day. Tips to add more fiber:
- Choose whole grains with 3–5 g fiber per serving. Look for whole grain breads, brown rice and oats, and consume the whole intact grain versus milled.
- Enjoy a vegetable or fruit serving with each meal or snack.
- Add beans to soups, stews, pastas, omelets, salads and casseroles.
- Have oatmeal versus dry cereal at breakfast, and toss in some whole fruit chunks or berries.
- For sandwiches, add bulk (no pun intended) with lettuce, tomato, cucumbers, peppers and other garden favorites. If you’re not a vegetable eater, getting them on your sandwich makes them easier to consume.
- Prefer a grain at snack time? Try popcorn versus crackers.
A Quick Guide to Fiber Counts
Here’s a reference that will give you and your clients a good idea of how much fiber is in some popular foods.
Want to find out more about nutrition? Check out the NASM Fitness Nutrition Specialization (FNS).
Duyff, R. L. 2012. American Dietetic Association Complete Food and Nutrition Guide (Revised and updated 4th ed.). Boston: Houghton Mifflin Harcourt.
Eat Right. Website. Academy of Nutrition and Dietetics. http://www.eatright.org
Fruits and Veggies More Matters. Website. Produce for Better Health Foundation. http://www.fruitsandveggiesmorematters.org
Hoy, M.K., & Goldman, J.D. 2014. Food Surveys Research Group Dietary Data Brief No. 12. Accessed July 20, 2017. www.ars.usda.gov.