Increased dietary fiber intake from either a high-fiber diet or supplementation plays little role in improving glycemic control in type 2 diabetes (T2D), according to study results presented during the American Diabetes Association’s 80th Scientific Sessions, held online from June 12 to 16, 2020.

Researchers conducted a 12-week, randomized, open-label, comparator-controlled study to examine the effects dietary fiber on glycemic control in 72 patients with T2D. All patients were overweight and received metformin therapy.

The participants were randomly assigned 1:2:1 to an intensive nutrition program including a high-fiber diet, dietary fiber supplements, or standard diet. Dieticians reinforced dietary recommendations in all 3 groups on a monthly basis. The study groups were similar with regard to age, body mass index, metformin intake, hemoglobin A1c (HbA1c), and initial fiber and calorie intake at baseline.

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Biochemical and anthropometric measurements taken at baseline and 12 weeks displayed significant improvements in HbA1c and body weight in all 3 groups, with no between-group differences in the magnitude of changes. Mean HbA1c decreased from 7.1%±0.5% to 6.6%±0.6% in the high-fiber diet group, from 7.1%±0.5% to 6.8%±0.5% in the fiber supplement group, and from 7.2%±0.4% to 6.7%±0.5% in the group that followed standard diet recommendations (P <.001 for all), and mean body weight decreased by 2.1±2.6 (P <.0001), 1.0±1.8 (P <.05), and 1.1±2.1 kg (P <.05), respectively.

Compared with the standard diet group, dietary fiber intake increased significantly in the high-fiber diet and fiber supplementation groups, but was not found to be associated with HbA1c. Calorie intake, however, was significantly associated with reductions in HbA1c in all 3 groups (r =0.307; P <.01).

“[O]ur study suggested that rather than fiber intake, caloric restriction followed by moderate weight loss is the main driver for glycemic improvement in overweight patients with T2D,” concluded the investigators.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Tramontana F, Maddaloni E, Greci S, et al. The effect of dietary fiber in combination with metformin therapy in type 2 diabetes. Presented at: American Diabetes Association 80th Scientific Sessions; June 12-16, 2020. Abstract 227-OR.

This article originally appeared on Endocrinology Advisor