Effects of a slowly fermentable fiber mixture against the background of a high-protein diet - on insulin sensitivity and metabolic health in individuals with overweight - a randomized, placebo-controlled trial

Sep 28, 2026

Uploaded by Sarah

A 12-week randomized, placebo-controlled trial evaluated whether daily supplementation with a slowly fermentable fiber mixture (potato fiber and sugar beet pectin) added to a high-protein diet improves insulin sensitivity and metabolic health in adults with overweight. Participants received fiber (n=19) or maltodextrin placebo (n=21). Peripheral insulin sensitivity decreased after fiber vs placebo (p=0.081) and whole-body insulin sensitivity significantly decreased (p=0.034), with reduced metabolic flexibility. Fiber mitigated insulin-mediated carbohydrate oxidation and fat oxidation changes seen with placebo, prevented increased protein oxidation, but increased colonic permeability and plasma interleukin-6. Body composition, microbiome composition, and fecal/circulating metabolites were unchanged.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages18

Reading Time45 min

AccessFree to download

Abstract

Trial design and outcomes

Metabolic effects and insulin sensitivity

Gut permeability, inflammation, and microbiome results

Conclusion

GUT MICROBES 2026, VOL. 18, NO. 1, 2606473 [https://doi.org/10.1080/19490976.2025.2606473](https://doi.org/10.1080/19490976.2025.2606473) RESEARCH ARTICLE Effects of a slowly fermentable fiber mixture against the background of a high-protein diet on insulin sensitivity and metabolic health in individuals with overweight: a randomized, placebo-controlled trial Colin A. J. van Kalkerena , Thirza van Deurena , Miranda M. J. Coenjaerdsa, b , Gianluca Galazzoc , David J. M. Barnettc , John Pendersc , Bolette Hartmannd , Jens J. Holstd , Emanuel E. Canforaa and Ellen E. Blaaka aDepartment of Human Biology, NUTRIM ‘Institute of Nutrition and Translational Research in Metabolism’, Maastricht University Medical Center+, Maastricht, The Netherlands; bDepartment of Nutrition and Diet, Maastricht University Medical Center+, Maastricht, The Netherlands; cDepartment of Medical Microbiology, NUTRIM ‘Institute of Nutrition and Translational Research in Metabolism’, Maastricht University Medical Center+, Maastricht, The Netherlands; dDepartment of Biomedical Sciences, NNF Center for Basic Metabolic Research, The Panum Institute, University of Copenhagen, Copenhagen, Denmark ABSTRACT The gut microbiota ferments dietary fibers, producing short-chain fatty acids (SCFA) . Enhanced SCFA production in the distal colon has been linked to improved cardiometabolic health. However, most fibers are fermented proximally, resulting in increased protein fermentation distally, producing metabolites putatively harmful to metabolic health. This 12-week randomized, placebo-controlled trial aimed to improve metabolic health through increasing distal SCFA production while inhibiting proteolytic fermentation using a fiber supplement that increased distal SCFA production in vitro. We assessed the effects of daily potato fiber/sugar beet pectin supplementation (fiber, n = 19) versus maltodextrin (placebo, n = 21), both added to a high-protein diet (25E% protein, ±45% plant-based), on peripheral insulin sensitivity (IS) in adults with overweight/obesity. Secondary outcomes included tissue-specific IS, body composition, microbial composition and functionality, substrate metabolism, and gut permeability. Peripheral IS tended to decrease after fiber supplementation compared to placebo (p = 0.081), while whole-body IS significantly decreased (p = 0.034) . Fiber mitigated the increase in insulin-mediated carbohydrate oxidation (p = 0.027) and decrease in fat oxidation (p = 0.006) that occurred in the placebo group. Additionally, fiber prevented an increase in protein oxidation (p = 0.048), while increasing colonic gut permeability (p = 0.046) and plasma interleukin-6 (p = 0.025) . Body composition, microbial composition, and fecal and circulating metabolites remained unchanged. In conclusion, fibers combined with a high-protein diet reduced (peripheral) IS and decreased metabolic flexibility compared to placebo. Reduced protein oxidation after fiber may reflect diminished amino acid bioavailability. Additionally, coadministration of fiber and protein may compromise gut barrier function and inflammatory responses. More research investigating the interplay between dietary fibers and proteins is needed. ARTICLE HISTORY Received 8 October 2025 Revised 19 November 2025 Accepted 15 December 2025 KEYWORDS Dietary fiber; insulin resistance; cardiometabolic health; microbiome; fermentation Introduction The rising prevalence of obesity and obesity-related diseases, including type 2 diabetes (T2D), poses an increased burden on healthcare systems worldwide. Accumulating evidence suggests that the microbiome may play a prominent role in these diseases, 1-5 being responsible for the fermentation of undigested food in the colon, including dietary fibers and proteins. Fermentation of dietary fibers produces short-chain fatty acids (SCFA), which can positively affect cardiometabolic health, improving multiorgan insulin resistance and reducing inflammation,

FAQs

What intervention and control were used in the trial?

Participants consumed daily potato fiber/sugar beet pectin supplementation as the fiber group (n=19) or maltodextrin as placebo (n=21), both added to a high-protein diet for 12 weeks.

How did the fiber mixture affect insulin sensitivity?

Peripheral insulin sensitivity tended to decrease with fiber compared with placebo (p=0.081), while whole-body insulin sensitivity significantly decreased (p=0.034).

What effects did the fiber mixture have on gut barrier function and inflammation?

Fiber prevented an increase in protein oxidation but increased colonic gut permeability (p=0.046) and raised plasma interleukin-6 (p=0.025), suggesting compromised barrier function and inflammatory responses.

Sep 28, 2026

Uploaded by Sarah