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Fiber For Fat Loss & Health – Ultimate Guide


Fiber is an essential nutrient that is often just viewed as something that should be consumed, without appreciating its integral role in digestive health, promotion of healthy bacteria and ability to help regulate appetite.

So, for these and other reasons, fiber should actually form a vital part of your diet, becoming an even more important component when attempting to lose weight.

In this guide, I breakdown the different types of fiber and their specific roles. Additionally, I’ll explain how increasing your fiber intake can play a serious part in your ability to manage and lose weight easily and effectively.

Fiber Types & Their Function

In the world of dietary fiber, we deal with two distinct forms known as insoluble and soluble. If you’ve ever taken a biology or chemistry course, you will probably know that soluble means mixing well with and absorbing water, while insoluble is basically the opposite.

Soluble Fiber

As mentioned, this form of fiber is able to be dissolved in and absorbs water. In doing so, this form of fiber forms a gel-like substance in the gut, which means it slows the rate of digestion.

As we’ll touch on in more depth shortly, this type of fiber can play a major role in reducing appetite. Since digestion is slowed, foods remain higher in the gut and stomach for longer periods of time, helping to reduce future appetite.

Insoluble Fiber

As the name suggests, insoluble fiber is not readily absorbed in water and typically moves through the gastrointestinal tract in a fairly undigested state. A primary reason for this is that, for the most part, humans lack the necessary enzymes to breakdown and digest insoluble fiber.

Typically, insoluble fiber is consumed to add bulk to stool and speed up the rate of motility through the digestive tract.

Lastly, the ingestion of insoluble fiber typically feeds beneficial bacteria in the gut. Since it can reach lower portions of the intestine in a relatively undigested state, it also acts as a fuel source for gut bacteria helping them to survive and even thrive.

Fiber Reduces Food Intake

Even though improved digestion is the number one benefit for which fiber is known, it is also one of the best nutrients you can ingest if you’re hoping to lose weight. Since fiber can slow digestion, it can also help regulate appetite, allowing you to consume fewer calories throughout the day’s meals (1, 2, 3).

Soluble fiber is particularly adept at helping curb appetite primarily due to its ability to absorb water. After ingestion, soluble fiber absorbs water and actually forms a gel-like substance in the stomach and upper intestine. In doing so, it significantly reduces the speed at which food travels through the gut.

Interestingly, this not only slows the speed but can also help to inhibit release of the hunger hormone, ghrelin.

Ghrelin is a hormone that is released by cells within the digestive tract, in particular the stomach. This hormone is released on a schedule of normal eating times and acts on the brain to encourage you to forage for and eventually ingest food (4, 5).

Unfortunately for ghrelin, the cells that secrete this hormone are actually sensitive to being stretched, as is the case when food has filled the stomach. Once stretched, release of the hormone is inhibited, allowing you to feel full and stop eating (6).

When soluble fiber is ingested and food motility is slowed, the amount of time that these cells are stretched is also prolonged, meaning that ghrelin secretion is reduced.

As a result, you feel fuller for much longer which can moderate food intake with ease, potentially leading to weight loss.

Fiber’s Additional Benefits

In addition to fiber’s effect on digestion and appetite, regular fiber ingestion may prove useful for regulating insulin and blood sugar as well.

One of the hallmarks of metabolic disease is insulin resistance, a disorder where chronic elevations of blood glucose and insulin prevent the body from using insulin appropriately. This issue is serious and can lead to obesity and even diabetes (7, 8, 9).

Fortunately however, increasing fiber intake may be a potential method for reducing this possibility.

Much like its effect on ghrelin, the slowed digestion of food can also limit insulin secretion. This is primarily because the rate of glucose entering the blood can be slowed significantly, leading to a smaller and slower release of insulin.

Another potential benefit as mentioned earlier is fiber’s ability to feed beneficial bacteria in the gut. Since many insoluble fibers can make it deep into the intestine where these bacteria reside, they can also feed them, allowing for continued growth.

This is especially beneficial since studies are beginning to reveal that a healthy gut microbiome may play a significant role in ailments such as depression, immune system issues and even weight loss (10, 11, 12, 13).

Common Fiber Sources & Best Practices

Just talking about fiber isn’t really going to help you unless you can identify the fiber foods to eat. In order to reap the benefits, you need to know what the best sources are and how to actually begin incorporating them into your diet.

Below is a list of some of the best sources for fiber: 

Ingredient Amount Grams of Fiber Total Calories
Medium Avocado 1 10 g 234 kcal
Psyllium Husk 20 grams 16 g 76 kcal
Chia Seeds 2 Tbsp. 10 g 120 kcal
Flax Seed 2 Tbsp. 10 g 140 kcal
Raspberries 1 cup 8 g 64 kcal
Asparagus 2 cup 6 g 54 kcal
Black Beans 1 cup 12 g 240 kcal
Lentils 1 cup 16 g 230 kcal
Canned Peas 1 cup 12 g 180 kcal

As you can see, the list of fibrous foods can be quite extensive. There are many other options, of course, but these should provide a good starting point. The soluble fiber source psyllium is a common fiber supplement.

Some of the sources provide both soluble and insoluble fiber, e.g. soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas and some fruit and vegetables; insoluble fiber foods include wheat bran, beans, lentils, vegetables, flax seed and whole grains.

When it comes to increasing your fiber intake, doing so is actually quite easy.

Some of these foods, such as Asparagus or Black beans are typically consumed with other foods, such as in a side dish. I suggest attempting to add at least 1 fibrous vegetable as a side dish for most meals. Simply adding a salad or a cup of other fibrous vegetables can allow for a significant increase.

Other fiber sources are actually great additives to other foods. Things like raspberries, chia and flax seeds can be added to foods such as Greek yogurt for a high protein and high fiber meal.

Finding ways to add these ingredients is typically quite easy and straightforward. I suggest experimenting with some of these ingredients to find what works best for you.

Fiber For Fat Loss & Health – Ultimate Guide

Even though you may not be concerned about fiber, if you care about your digestive health and ability to manage hunger, you certainly should start to take an interest in fiber.

Fiber is effective at improving digestive health, but can also significantly reduce appetite, due to slowing the rate of digestion.

Further, finding different ways to incorporate more fiber in your diet will be beneficial to improve health and fitness. Doing so can significantly increase your fiber intake with relatively little effort.


  1. Bolton, R. P., Heaton, K. W., & Burroughs, L. F. (1981). The role of dietary fiber in satiety, glucose, and insulin: studies with fruit and fruit juice. The American journal of clinical nutrition, 34(2), 211-217.
  2. Cho, S. S., Case, I. L., & Nishi, S. (2009). Fiber and Satiety. Weight Control and Slimming Ingredients in Food Technology, 227.
  3. Lefranc-Millot, C., Macioce, V., Guérin-Deremaux, L., Lee, A. W., & Cho, S. S. (2012). Fiber and Satiety. Dietary Fiber and Health, 83.
  4. Lesauter, J., Hoque, N., Weintraub, M., Pfaff, D. W., & Silver, R. (2009). Stomach ghrelin-secreting cells as food-entrainable circadian clocks. Proceedings of the National Academy of Sciences, 106(32), 13582-13587. doi:10.1073/pnas.0906426106
  5. Cummings, D. E., Purnell, J. Q., Frayo, R. S., Schmidova, K., Wisse, B. E., & Weigle, D. S. (2001). A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes, 50(8), 1714-1719.
  6. Sakata, I., & Sakai, T. (2010). Ghrelin cells in the gastrointestinal tract. International journal of peptides, 2010.
  7. Boden, G. (1996). Fatty acids and insulin resistance. Diabetes care, 19(4), 394-395.
  8. Hua, C. H., Liao, Y. L., Lin, S. C., Tsai, T. H., Huang, C. J., & Chou, P. (2011). Does supplementation with green tea extract improve insulin resistance in obese type 2 diabetics? A randomized, double-blind, and placebocontrolled clinical trial. Alternative Medicine Review, 16(2), 157-163.
  9. López-Alarcón, M., Perichart-Perera, O., Flores-Huerta, S., Inda-Icaza, P., Rodríguez-Cruz, M., Armenta-Álvarez, A., … & Mayorga-Ochoa, M. (2014). Excessive refined carbohydrates and scarce micronutrients intakes increase inflammatory mediators and insulin resistance in prepubertal and pubertal obese children independently of obesity. Mediators of inflammation, 2014.
  10. Angelakis, E., Merhej, V., & Raoult, D. (2013). Related actions of probiotics and antibiotics on gut microbiota and weight modification. The Lancet infectious diseases, 13(10), 889-899.
  11. Dinan, T. G., & Quigley, E. M. (2011). Probiotics in the treatment of depression: science or science fiction?. Australian & New Zealand Journal of Psychiatry, 45(12), 1023-1025.
  12. Lescheid, D. W. (2014). Probiotics as regulators of inflammation: A review. Functional Foods in Health and Disease, 4(7), 299-311.
  13. Kang, E. J., Kim, S. Y., Hwang, I. H., & Ji, Y. J. (2013). The effect of probiotics on prevention of common cold: a meta-analysis of randomized controlled trial studies. Korean journal of family medicine, 34(1), 2-10. 


About the author

Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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