High-Fiber Diet Shows Better Blood Sugar Control Than Metformin in 84-Day Clinical Trial

Could eating more fibre help control type 2 diabetes and obesity more effectively than medication alone? A new clinical trial suggests that a targeted high-fibre diet may improve blood sugar levels, body weight and gut health, with some outcomes showing greater improvements than those observed with metformin treatment.

Published in Frontiers in Microbiology, the study investigated the effectiveness of a high-fibre dietary intervention compared with metformin monotherapy among adults with newly diagnosed type 2 diabetes and obesity, a combination sometimes referred to as diabesity.

Researchers at Henan Provincial People's Hospital in China conducted an 84-day randomised clinical trial involving 48 adults aged 18 to 70 years, of whom 46 completed the study.

Participants were assigned to either a high-fibre diet without medication or metformin treatment.

The dietary intervention included soluble and insoluble fibres such as inulin and resistant dextrin, which can influence gut bacteria involved in metabolism and blood sugar regulation.

The findings revealed that after 84 days, participants following the high-fibre diet had a baseline-adjusted average HbA1c of 6.3%, compared with 6.7% in the metformin group.

Importantly, the high-fibre group also demonstrated a lower average body mass index of 28.4 kg/m², compared with 30.2 kg/m² among participants receiving metformin.

Researchers observed improvements in blood sugar variability, body fat and triglyceride levels among those following the dietary intervention.

Analysis of gut bacteria revealed increased levels of beneficial microorganisms, including Bifidobacterium and Lactobacillus, alongside reductions in certain bacteria associated with inflammation.

These microbial changes appeared within 28 days of starting the high-fibre intervention.

However, researchers noted that lower calorie intake in the dietary group may have contributed to the metabolic improvements.

The study was also limited by its small sample size, unequal treatment groups and short follow-up period.

The findings suggest that targeted fibre-rich dietary interventions may support diabetes and obesity management.

REFERENCE: Li, Y., Liu, Y., Chen, Y., et al. (2026). High-fiber diet altered gut microbiota, improved glycemic control, and reduced body weight in newly diagnosed type 2 diabetes and obesity. Frontiers in Microbiology 17. DOI: 10.3389/fmicb.2026.1972983.