Body mass index, physical activity and dietary behaviours among adolescents in the Kingdom of Tonga.

OBJECTIVES: To compare the prevalence of overweight and obesity among adolescents using international and ethnic-specific cut-off points and to examine patterns of physical activity and dietary behaviours. DESIGN: Cross-sectional analytical study. SETTING: Schools on Tongatapu, Vava'u and Hapa'ai islands in the Kingdom of Tonga. SUBJECTS: A total of 443 school students aged 11-16 years underwent anthropometric measures of height and weight and provided self-reported measures of physical activity and dietary behaviours. Results Mean body mass index (BMI) was higher among girls than boys (23.7 kg m(-2) vs. 21.8 kg m(-2) and tended to increase with age. A total of 36.0% of boys and 53.8% of girls were overweight or obese using the international cut-off points, whereas 25.0% of boys and 37.6% of girls were classified in this way using Polynesian-specific cut-off points. Tinned mutton or beef was the food that most participants (56.9%) reported eating once or more per day. Over half of the young people did not eat taro, fruit or vegetables at least once per day. Regular physical activity outside of school hours was reported by 20.7% of respondents, and 58.2% watched 1 h or more of television per day. Physical activity participation was the only behaviour independently associated with a lower risk of overweight or obesity. Conclusions Using Polynesian-specific cut-off points for overweight and obesity the prevalence of these conditions was still among the highest found in adolescents. The prevalence of physical inactivity and poor dietary habits indicate that risk factors for chronic disease are well established during adolescence in Tonga.