Change in food patterns of Tehrani adults and its association with changes in their body weight and body mass index in District 13 of Tehran: Tehran Lipid and Glucose Study

Dietary determinants of weight gain remain controversial. The assessment of dietary patterns has been increasingly used as an alternative to nutrient- or food-based analysis. The aim of this study was to determine the association between changes in food patterns and changes in body weight and body mass index in a group of Tehrani adults. As part of the Tehran Lipid and Glucose Study, a total number of 82 men and 124 women (≥18 years old) were followed up between 1999-2001 and 2004-2007; the mean follow-up period was 6 years. They were divided into two groups: normal weight (BMI<25) and overweight/obese (BMI25). Dietary intake was assessed using a food frequency questionnaire and two 24-hour dietary recalls. The food items were divided into 21 groups according to their nutrients contents. Food patterns were derived by factor analysis at each time interval. Changes in food patterns, weight and BMI were calculated by subtracting the factor scores of each food pattern, weight and BMI in the first period from their respective values in the second period. The mean ages of the men and women at the beginning of the study were 45±11 and 39±14 years, respectively. Three food patterns were identified in the two periods of the study, with a total variance of 29 and 33%, respectively: “healthy”, “western”, and “mixed”. In both periods, refined grains, salty snacks, sauces, fast foods, processed meat products and sweetened beverages were the major contributors to the western dietary pattern, while the healthy pattern included vegetables, fruits, poultry and fish, dairy products and whole grains. There were no significant differences in the mean delta factor scores of the healthy and the western dietary patterns between men and women. In a multivariate adjusted model, after adjusting for confounding factors (β=0.32, R2=0.25, P<0.001), the strongest predictor of a change in body weight was a change to the western food pattern as compared to healthy dietary pattern. In addition, based on multiple regression analysis, changing to the western pattern caused a higher increase in BMI in overweight/obese individuals than in those with a normal weight (β=0.41, R2=0.22, p<0.001). Adherence to the western food pattern was associated with changes in body weight and BMI. This effect was greater in overweight/obese individuals.