Glycaemic index (GI) reflects the postprandial glucose response of carbohydrate-containing foods. A diet with lower GI may improve glycaemic control in people with diabetes. The purpose of the present study was to evaluate the change in outcomes following a behavioural intervention which promoted lower-GI foods among adults with diabetes.

A pre-test–post-test control group design was used with participants randomly assigned to an immediate (experimental) or delayed (control) treatment group. The intervention included a 9-week, group-based intervention about carbohydrate and the glycaemic index. Dietary, anthropometric and metabolic measures were obtained pre/post-intervention in both groups and at 18-week follow-up for the immediate group.

The study was conducted in a rural community in the north-eastern USA.

Adults having type 2 diabetes mellitus for ≥1 year, aged 40–70 years and not requiring insulin therapy (n 109) were recruited.

Following the intervention, mean dietary GI (P < 0·001), percentage of energy from total fat (P < 0·01) and total dietary fibre (P < 0·01) improved in the immediate compared with the delayed group. Mean BMI (P < 0·0001), fasting plasma glucose (P = 0·03), postprandial glucose (P = 0·02), fructosamine (P = 0·02) and insulin sensitivity factor (P = 0·04) also improved in the immediate group compared with the delayed group. Mean waist circumference among males (P < 0·01) and body weight among males and females (P < 0·01) were significantly different between treatment groups.

Educating clients about carbohydrate and the glycaemic index can improve dietary intake and health outcomes among adults with type 2 diabetes.

Traditionally, carbohydrate has been the largest contributor to energy intake among people with diabetes, yet different carbohydrate foods produce different glycaemic responses. Glycaemic load represents the total glycaemic effect of the diet and influences glycaemic control. Adequate self-efficacy and outcome expectations are needed to change carbohydrate intake and to evaluate relevant interventions. The purpose of this research was to develop and test instruments regarding self-efficacy and outcome expectations for the adoption of a lower glycaemic load diet.

Participants completed each instrument at their convenience and mailed the instruments to the investigators.

A community sample of individuals 21–75 years of age with type 2 diabetes for ≥ 1 year (n = 108) was recruited.

Principal components analysis revealed three factors on the self-efficacy questionnaire: glycaemic index, negative food selection and self-regulation efficacy which accounted for 62% of the variance in these items. The outcome expectations instrument yielded three factors: barriers to dietary change and glycaemic control, and family support expectations which accounted for 48% of the variance. Coefficient α for each construct was >0.70 and coefficient H for each construct was ≥ 0.80.

The two instruments developed for this study can provide important insights about the self-efficacy and outcome expectations regarding the quantity and quality of carbohydrate consumed and self-monitoring performed for diabetes management. Future research is needed to evaluate the relationship among these constructs, dietary intake and glycaemic control.