To investigate the association of major dietary patterns with the risk of impaired glucose and insulin homeostasis during a 3-year follow-up.

Fasting serum insulin (FSI), fasting (FSG) and 2 h serum glucose (2h-SG) were measured at baseline and again after 3 years. Dietary intakes were evaluated using a validated 168-item semi-quantitative FFQ and major dietary patterns were obtained using principal component analysis. Logistic regression models were used to estimate the occurrence of impaired fasting glucose (IFG), impaired glucose tolerance (IGT), pre-diabetes (IGT/IFG), β-cell dysfunction and hyperinsulinaemia across tertiles of dietary patterns, with adjustment for potential confounding variables.

Tehran Lipid and Glucose Study.

Iranian men and women (n 904).

Mean age of participants was 38·7 (sd 11·3) years and 44·6 % were men. Major dietary patterns were Western, traditional and healthy, which explained 25·2 % of total variance in food intake. There was a positive association between Western and traditional scores with 3-year change in 2h-SG, while the healthy pattern was negatively related to 3-year changes in FSG, 2h-SG, FSI and homeostasis model assessment of insulin resistance. Highest compared with the lowest tertile of the Western dietary pattern was accompanied by a higher risk for development of IGT (OR=3·09; 95 % CI 1·28, 7·50); a higher score on the healthy dietary pattern was associated with a significantly reduced risk of hyperinsulinaemia (OR=0·53; 95 % CI 0·28, 0·94).

Our findings showed that adherence to a Western dietary pattern may be a risk factor for the development of IGT, while a healthy dietary pattern may prevent hyperinsulinaemia.