Association between dietary phytochemical index and 3-year changes in weight, waist circumference and body adiposity index in adults: Tehran Lipid and Glucose study

Background: High intakes of phytochemical-rich foods have favorable effects on the prevention of chronic diseases. In this study we assessed the dietary phytochemical index (PI) in relation to 3-year change in weight, waist circumference (WC), body adiposity index (BAI) among Tehranian adults. Methods: This longitudinal study was conducted in the framework of Tehran Lipid and Glucose Study, between 2006-2008 and 2009-2011, on 1938 adults, aged 19-70 y. The usual intake of participants was measured at baseline using a validated semi-quantitative food frequency questionnaire and dietary PI was calculated. Anthropometric measures were assessed both at baseline and 3 years later. Multiple regression models were used to estimate mean difference changes in anthropometrics associated with various dietary PI. Results: The mean age of participants was 40.4 +/- 13.0 y, at baseline, respectively. Mean weight gain was 1.49 +/- 5.06 kg (1.65 +/- 5.3 kg in men and 1.34 +/- 4.9 kg in women) during 3-year period. After adjustment for potential confounding variables including age at baseline, sex, BMI, educational levels, smoking, physical activity, total energy intake, dietary intake of carbohydrate, fat and protein, dietary intakes of whole grains in the highest quartile category of PI were inversely associated with 3-year changes in weight and WC (P for trend <0.05). Dietary intake of fruits in the highest quartile was also associated with lower weight gain during the study period (P for trend <0.05). There was significant inverse association between the highest quartile category of dietary PI with the 3-year changes in weight and BAI (P for trend <0.05). Conclusion: Higher dietary PI could have favorable effects on prevention of weight gain and reduction of body adiposity in adults.