Background
Urbanisation has been reported to have negative effects on lifestyle and possibly on body composition. The aim of this study was to assess the effect of urbanization on dietary patterns and measures of body composition in Sri Lankan adolescent girls.

Methods
Body Mass Index was calculated in 552 adolescent school dropouts. Percentage body fat was calculated using a population specific skin fold thickness equation. Dietary patterns were identified based on information obtained from a food frequency questionnaire. Extraction of factors of the dietary patterns was by principal component analysis. The sum of hours / week spent on physical activity was calculated. Focus group discussions were held to gather supportive qualitative data on food related behaviors. Multivariate linear regression models were used to assess the association between independent variables and dietary patterns.

Results
Two dietary patterns were identified; a convenience-based dietary pattern with higher factor loadings for starchy foods other than rice, animal foods, dairy products, fruits, sweetened food and fried food, and a traditional pattern with higher factor loadings for rice, tubers and potatoes, vegetables and dark green leafy vegetables. An urban girl had greater than three times the risk of having a higher percentage body-fat than a rural girl (P = 0.01, OR = 3.2). Time spent on physical activity was significantly (P = 0.003) higher among the rural girls. Focus group discussions indicate that urban girls preferred food from vendors due to convenience while rural girls preferred home cooked meals.

Conclusions
Urban adolescents in this study followed a convenience based dietary pattern and this dietary pattern and lower physical activity was associated with overweight and higher body fat.