The aim of the present study was to assess the reliability, comparative validity and stability of dietary patterns defined by factor analysis for participants of the Tehran Lipid and Glucose Study. A total of 132 subjects, aged $ 20 years, completed a 168-item FFQ (FFQ1, FFQ2) twice, with a 14-month interval. Over this duration, twelve dietary recalls (DR) were collected each month. To assess the stability of the FFQ, participants completed the third FFQ (FFQ3) after 8 years. Following these, two dietary patterns -the 'Iranian Traditional' and the 'Western' -were derived from FFQ1 and FFQ2 and the mean of DR (mDR); and three dietary patterns were identified from FFQ3: the 'Iranian Traditional', the 'Western' and the 'Combined'. The reliability correlations between factor scores of the two FFQ were 0·72 for the Iranian Traditional and 0·80 for the Western pattern; corrected month-to-month variations of DR correlations between the FFQ2 and mDR were 0·48 for the first and 0·75 for the second pattern. The 95 % limits of agreement for the difference between factor scores obtained from FFQ2 and mDR lay between 2 1·58 and þ 1·58 for the Iranian Traditional and between 21·33 and þ1·33 for the Western pattern. The intra-class correlations between FFQ2 and FFQ3 were 20·09 (P¼0·653) and 0·49 (P , 0·001) for the 'Iranian Traditional' and the 'Western', respectively. These data indicate reasonable reliability and validity of the dietary patterns defined by factor analysis. Although the Western pattern was found to be fairly stable, the Iranian Traditional pattern was mostly unstable over the 8 years of the study period.

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Summary Objectives: Using a dietary pattern analysis method could provide more information about the nutritional etiology of chronic diseases such as obesity. The aim of this study is to determine the association between major dietary patterns and general and central obesity among adult women living in Tehran. Materials and methods: A cross-sectional study was conducted in Tehran, Iran, with 460 women aged 20-50 y. Dietary intake in the previous year was collected by a semi-quantitative food frequency questionnaire. Weight, height and waist circumstance (WC) were measured with standard methods and body mass index (BMI) was calculated. General obesity was defined as BMI Ն 30 kg/m 2 and central obesity as WC Ն 88 cm. Factor analysis was used for identifying major dietary patterns. The association between major dietary patterns and general and central obesity were assessed by logistic regression analysis. Results: Two major dietary patterns were extracted: "Healthy" and "Unhealthy" dietary patterns. After adjusting for confounders, individuals in the highest quartile of the unhealthy dietary pattern score were more likely to have general (OR ϭ 7.33, 95% CI: 2.39-22.51) and central obesity (OR ϭ 4.99, 95% CI: 2.08-11.94), whereas, those in the upper quartile of healthy dietary pattern were less likely to have general (OR ϭ 0.38, 95% CI: 0.15-0.98) or central obesity (OR ϭ 0.33, 95% CI: 0.16-0.71). Conclusion: Our data suggest that a dietary pattern rich in fruit, vegetables, low-fat dairy products and poultry might be negatively associated with obesity. Furthermore our data showed that a dietary pattern high in processed meats, soft drinks, sweets, refined grains, snacks and processed juice might be positively associated with obesity among women aged 20-50 y.