Association between dietary fibre:carbohydrate intake ratio and insulin resistance in Japanese adults without type 2 diabetes

An easily understandable index that measures the quality of carbohydrate may aid people in adopting dietary habits that improve their glucose tolerance. We aimed to evaluate the relationship between a ratio of dietary fibre to carbohydrate intakes (fibre:carbohydrate ratio (F:C-R)) and glucose tolerance cross-sectionally and longitudinally. Subjects were 190 Japanese men and women without type 2 diabetes (mean age 55.4 years) who participated in a 5-month diet and exercise programme. We compared baseline anthropometric, dietary and metabolic profiles between those with higher F:C-R and those with lower ratios. Multivariable regression analyses were performed to examine the associations between the F:C-R and homoeostasis model of assessment for insulin resistance (HOMA-IR) and HbA1c at baseline and between changes in the F:C-R and changes in HOMA-IR and HbA1c over the 5-month period. At baseline, the higher F:C-R group had significantly lower body weight, lean body mass, fasting insulin level and HOMA-IR as compared with the lower F:C-R group. The two groups had similar intakes of carbohydrate and fat, whereas protein intake was greater in the high F:C-R group. Baseline F:C-R was not significantly associated with HOMA-IR or HbA1c at the beginning of the study in multivariable models. Increases in the ratio during the 5-month programme was associated with reductions in HbA1c (P<0.001). These findings highlight the potential utility of the F:C-R in strategies aimed at type 2 diabetes prevention.