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Characteristics of Eating Habits and Physical Activity in Relation to Body Mass Index Among Adolescents

Objective: To assess eating habits and the level of physical activity in adolescents and develop a predictive model for the body mass index (BMI) based on these variables. Design: In this cross-sectional study, eating habits and the level of physical activity were assessed using a questionnaire validated in adolescents. Body mass and height collected during the last annual checkup were extracted from personal medical records. Subjects: The sample included 330 boys and 377 girls (mean age 15.8 ± 0.2 years) who were first-year high school students in the city of Belgrade, Serbia. Measures: Responses to each of the 14 questions about eating habits and 6 questions about physical activity were scored from the least (0) to the most (3) desired behaviors. These ratings were then averaged to arrive to an aggregate score for each domain. The BMI was calculated according to the standard method. A series of regression analyses was performed to derive the best model for predicting BMI in boys and girls based on individual eating habits and physical activity items, first separately and then combined. Results: In the sample, 24.5% of boys and 9.5% of girls were overweight or obese. Girls’ eating habits were better than boys (mean aggregate score 2.3 ± 0.3 and 2.1 ± 0.3, respectively, p < 0.001), whereas the level of physical activity was greater in boys than girls (2.1 ± 0.6 vs 1.9 ± 0.6, p < 0.001). The differences between boys and girls in the BMI, eating habits, and physical activity remained significant after controlling for their knowledge about healthy eating and education level of their parents. Eating habits were a better predictor of BMI than physical activity, particularly in boys (R 2 = 0.13 vs R 2 = 0.02) compared to girls (R 2 = 0.04 vs R 2 = 0.01). Combining eating habits and physical activity in the multivariate model of BMI resulted in a better predictive accuracy in boys (R 2 = 0.17) but not girls (R 2 = 0.04). Conclusions: Eating habits and physical activity differ between adolescent boys and girls and can predict BMI, particularly in boys. The results suggest the need to develop gender-specific programs for promoting healthy lifestyle among adolescents in our country.