Diabetes DPG Public Library

Prediabetes affects nearly half of all U.S. adults and is characterized primarily by insulin resistance, a condition in which the cells in the body fail to respond adequately to insulin, resulting in elevated blood glucose. Without intervention, up to 70% of individuals with prediabetes progress to type 2 diabetes.

This randomized controlled trial by Demmer et al. enrolled 77 overweight or obese sedentary adults with prediabetes. Participants were assigned either to a home-based moderate-intensity walking program, which includes three sessions per week with progressing activity level from 30 to 45 minutes per session over eight weeks, or to a control group maintaining their usual activity levels. Gut microbiome composition was assessed through stool samples at baseline, week 4, and week 8, while blood levels of short-chain fatty acids (SCFAs) were measured at baseline and week 8, which are metabolites produced when gut bacteria ferment dietary fiber that are known to support insulin sensitivity.

The walking group showed a modest but statistically significant decrease in gut microbial diversity by week 8. The authors interpret this cautiously, noting that comparable short-term diversity reductions have been observed following dietary fiber interventions and have in some cases coincided with improvements in metabolic health. At the functional level, the microbial changes suggested a more resilient, metabolically active microbiome.

No statistically significant differences were observed in SCFA levels, blood glucose, or insulin between groups. The authors conclude that larger, longer trials are needed to determine whether these gut microbiome shifts ultimately contribute to meaningful improvements in insulin resistance.