Glycaemic load is associated with insulin resistance in older Australian women

Diets with a high postprandial glycaemic response may contribute to the long-term development of insulin resistance and diabetes; however, earlier epidemiological studies are conflicting on whether glycaemic index (GI) or glycaemic load (GL) are dietary factors associated with the progression. Our objectives were to estimate GI and GL in a group of older women, and evaluate cross-sectional associations with insulin resistance.

The subjects were 329 Australian women aged 42-81 years participating in year 3 of the Longitudinal Assessment of Ageing in Women study. Dietary intakes were assessed by diet history interviews and analysed using a customized GI database. Insulin resistance was defined as a homeostasis model assessment value of >3.99, based on fasting blood glucose and insulin concentrations.

GL was significantly higher in the 26 subjects who were classified as insulin resistant compared with subjects who were not (134+/-33 versus 114+/-24, P<0.001). In a logistic regression model, an increment of 15 GL units increased the odds of insulin resistance by 2.09 (95% confidence interval (1.55, 2.80), P<0.001) independently of potential confounding variables. No significant associations were found when insulin resistance was assessed as a continuous variable.

The results of this cross-sectional study support the concept that diets with a higher GL are associated with an increased risk of insulin resistance. Further studies are required to determine whether reducing the glycaemic intake, either by consuming lower GI foods or through smaller serves of carbohydrate, can contribute to a reduction in development of insulin resistance and long-term risk of type II diabetes.