What is the Science Behind Fiber and Weight Loss?

You’ve heard it in the news, from your health-conscious friend, and from Dr. Oz: fiber is the weight-loss cure of your dreams.


But how exactly does fiber manage to do that? What is the science behind fiber and weight loss?


There are three key characteristics of fiber that promote weight loss: satiety, blood glucose management, and a healthy gut microbiome.


  1. Satiety

One of the major reasons is due to fiber’s ability to increase satiety; dietary fiber, both soluble and insoluble, promotes fullness post-meal, which prevents unnecessary snacking and eating (1). The reduction of extra calories from excessive snacking and eating significantly promotes weight loss. Plus, there is an added benefit of encouraging healthy eating habits.


Simply put: you eat less because you’re too full from your fiber-rich meal. And of course, if you decrease your overall caloric intake, especially from foods that aren’t nutritious and healthy, it is very probable that you will experience weight loss. 


  1. Blood glucose control

Another major reason is fiber’s role in blood glucose control (2-6). Especially for insoluble fiber, a high-fiber diet was shown to help stabilize blood glucose post-meal (3). When blood glucose increases, our pancreas produces insulin (7). Insulin signals our body to either use glucose as energy or store it as fat. If our body can’t control blood glucose, our body’s insulin production goes into overdrive, encouraging glucose to be stored at fat. Extra glucose stored as fat can lead to weight gain. Therefore, with fiber, you can better control blood glucose and slow glucose absorption to promote weight loss. 

  1. Healthy gut microbiome

Recently, numerous studies have suggested that a healthy gut microbiome promotes weight loss. And what is a crucial element for a healthy gut? Dietary fiber.

Fiber has the power to “increase the potentially beneficial bacterial genomes” and enrich the microbiome (8). As fiber feeds our gut bacteria, it can reverse dysbiosis (a microbial imbalance in the gut microbiota), while preventing obesity development and long-term weight gain (9,10). These studies not only showcase the effectiveness of dietary fiber in promoting weight loss, but also reevaluate the notion that weight loss is simply all about energy restriction, and pushes for personalized nutrition intervention according to one’s gut microbiota.

So, if you thought fiber couldn’t possibly be as powerful as they say, hopefully this convinced you otherwise. Check out our FYBR bars to test the science yourself!

Author: Haekyeung Kang, BS, Nutrition and Dietetics, NYU, 2017-2021


(1) Ma Y, Olendzki BC, Wang J, et al. Single-Component Versus Multicomponent Dietary Goals for the Metabolic Syndrome: A Randomized Trial. Ann Intern Med. 2015;162:248–257. doi: https://doi.org/10.7326/M14-0611

(2) Ellis, Esther. “What Is Glycemic Index?” EatRight, Nov. 2019, www.eatright.org/food/nutrition/dietary-guidelines-and-myplate/what-is-glycemic-index.

(3) T M Wolever, Relationship between dietary fiber content and composition in foods and the glycemic index, The American Journal of Clinical Nutrition, Volume 51, Issue 1, January 1990, Pages 72–75, https://doi.org/10.1093/ajcn/51.1.72

(4)Salmerón J, Manson JE, Stampfer MJ, Colditz GA, Wing AL, Willett WC. Dietary Fiber, Glycemic Load, and Risk of Non—insulin-dependent Diabetes Mellitus in Women. JAMA. 1997;277(6):472–477. doi:10.1001/jama.1997.03540300040031

(5) Matthias B Schulze, Simin Liu, Eric B Rimm, JoAnn E Manson, Walter C Willett, Frank B Hu, Glycemic index, glycemic load, and dietary fiber intake and incidence of type 2 diabetes in younger and middle-aged women, The American Journal of Clinical Nutrition, Volume 80, Issue 2, August 2004, Pages 348–356, https://doi.org/10.1093/ajcn/80.2.348

(6) Salmerón, Jorge, et al. “Dietary Fiber, Glycemic Load, and Risk of NIDDM in Men.” Diabetes Care, American Diabetes Association, 1 Apr. 1997, care.diabetesjournals.org/content/20/4/545.abstract.

(7) Wilcox, Gisela. “Insulin and insulin resistance.” The Clinical biochemist. Reviews vol. 26,2 (2005): 19-39.

(8) Filippo, Carlotta De, et al. “Impact of Diet in Shaping Gut Microbiota Revealed by a Comparative

Study in Children from Europe and Rural Africa.” PNAS, National Academy of Sciences, 17 Aug.

2010, https://www.pnas.org/content/107/33/14691.

(9) Rivera-Piza, A., Lee, S. Effects of dietary fibers and prebiotics in adiposity regulation via modulation of gut microbiota. Appl Biol Chem 63, 2 (2020). https://doi.org/10.1186/s13765-019-0482-9

(10) Menni, C et al. “Gut microbiome diversity and high-fibre intake are related to lower long-term weight gain.” International journal of obesity (2005) vol. 41,7 (2017): 1099-1105. doi:10.1038/ijo.2017.66