Introduction At present the potential public health issue that is emerging is the increasing incidence of childhood obesity in developing countries, and the resulting socioeconomic and public health burden that will be faced by these countries in the near future. The prevalence is higher in the urban than in the rural areas. Many studies have shown that the prevalence of overweight among adolescents varies between 10 and 30%.(1–11) Prevalence varies within the country because of differences in the lifestyle, mainly in the dietary patterns, and physical activity. In addition to this urbanization and industrialization are the main culprits for the increase in the prevalence of childhood obesity. No published literature can be found in this part of the country to assess the prevalence and determinants of obesity among adolescents. Studies of such a nature will be useful tools in planning and developing appropriate intervention methods. In this context, the present study has been conducted to estimate the prevalence and determinants of overweight and obesity among school children aged between 12 and 15 years, in a city in South Karnataka. Materials and Methods This was a school-based, cross-sectional study carried out over a period of four months, from January to April 2007. The sample size was estimated for infinite population by using the formula 4pq/d2 where prevalence was taken as 10%.(1) The required precision of the estimate (d) was set at 20%. Using the above-mentioned formula, the sample size was estimated to be 900. After adding the non-response error of 10%, an additional 100 subjects were included. Thus, 1000 subjects were selected for this study. We adopted a multistage stratified random sampling procedure. For the selection of schools, a list of all schools was obtained from the school authorities of the district education office. First, six schools were selected by a simple random technique. Probability, proportional to the size sampling technique was used to select the sample from each school. The subjects were adolescents, 12 to 15 years of age, in the city of Mangalore, Karnataka, a Southern State of India. After reaching the concerned school, the classes were selected randomly from each grade. Students were selected from each class by the simple random technique, using the students' register, till the desired sample from each class was met. It was assumed that from each institution, at least 50 subjects would be recruited from each class. If a designated student could not be contacted or was not cooperative during the three separate visits, the subject was considered as a non-respondent. Trained investigators weighed all of the adolescents without shoes and heavy clothing, using an electronic weighing scale with an error of ±100 g. The weighing scale was regularly checked with known standard weights. A portable anthropometric rod was used for measuring the height, with an error to the nearest of 0.1 cm, using standard procedures.(12) The International Obesity Task Force references were used to define overweight and obesity in this study.(13) Information was collected on physical activity, which included the mode of transport used to go to school and physical activities such as participation in sports and games, aerobic physical exercises, and frequency and duration of participation in household activities. Time spent in watching television and playing computer and video games were also noted. Diet preferences for chocolate, biscuits, chips, and colas were taken into consideration. Adolescents were categorized into two groups namely overweight (≥ wighty-fifth percentile) and obese (≥ ninety-fifth percentile). The socioeconomic status was assessed based on the Kuppuswamy classification. Univariate and Multiple Logistic Regression analyses were carried out. For all statistical tests, P 2 60 1 (1.7) 0 (0) TV, Computer watching in hrs 4 133 26 (19.5) 20 (15) Diet preferences Normal 710 52 (7.3) 14 (2.0) 98.35, 0.001* + chocolate 108 19 (17.6) 13 (12.0) + chocolate + biscuits 18 4 (22.2) 3 (16.7) + + chocolates + chips 41 9 (22.0) 8 (19.5) +cola 22 5 (22.7) 5 (22.7) * P value less than 0.05 is considered as significant. Table 2 Correlates of overweight and obesity; Multiple logistic regression analysis Variables Adjusted odds ratio 95% CI P value Socioeconomic status Grade 4 - - - Grade 1 2.09 1.1–4.0 0.02* Grade 2 1.64 0.8–3.3 0.17 Grade 3 0.99 0.42–2.32 0.98 TV, Computer watching in hrs 4 7.3 3.6–14.66 0.001* Diet preferences Normal - - - + chocolate 5.58 2.1–14 0.001* + chocolate + biscuits 1.3 0.5–3.8 0.6 + chocolates + chips 1.02 0.24–4.27 0.98 + cola 0.96 0.3–3.0 0.95 Physical activity duration in hrs >2 - - - 1-2 1.56 0.94–2.6 0.09 <1 21.09 2.77–166.8 0.003* * P value less than 0.05 is considered as significant Discussion The overall prevalence of overweight adolescents among the urban group was found to be 9.9%, which was consistent with a recent study.(2) However, the National Nutrition Monitoring Bureau surveys in 2002, in rural areas, reported the prevalence of as little as 0.6%.(3) A similar study done in Hyderabad showed that the prevalence of overweight was 7.2% among the 12 to 17 year age group.(4) Although, some other studies done in India showed a higher prevalence of overweight and obesity.(5–8) A study in Delhi on affluent school children showed the prevalence of obesity to be 7.4%.(9) Another study among affluent girls in Delhi reported the prevalence of obesity and overweight to be 5.3 and 15.2%, respectively.(10) Similar studies had been conducted to assess the prevalence of overweight and obesity in India and the results are comparable to our study, with respect to the prevalence of obesity.(11 14) A study done in USA during 2001–2002 showed the prevalence of overweight and obesity as 31.5 and 16.5%, respectively, for the 6 to 19 year age group.(15) The widely differing prevalence of overweight and obesity was due to the definitions used, age group and sex taken for the study, uniformity of selection of the sample, area selected, and the methodology used for the survey. Overweight and obesity were marginally higher in the pubertal age groups of 13 to 15 years, perhaps because of increased adipose tissue and overall body weight in children during puberty. One of the major reasons for childhood obesity was watching television or using computers as shown by another study.(4 16) A clear socioeconomic gradient in the prevalence of overweight and obesity was observed in this study, which was consistent with other studies.(4 5 17) The results revealed that regular physical activity was an important factor in reducing the prevalence of overweight and obesity, which was consistent with other studies.(4 5) We could not interview 100 non-respondents because of their non-availability during our field visits. As the proportion of non-respondents was within the limits, we expected only a minimal effect on our prevalence estimate. A normal diet survey was not performed because of feasibility constraints. It was concluded that the overall prevalence of overweight was 9.3% among boys and 10.5% among girls; 5.2 and 4.3% were obese, respectively. The prevalence of overweight was higher among the adolescents of the high socioeconomic status group, who had physical activity of < one hour/day, watched television ≥ 4 hours/day, and ate chocolates daily. Action needs to be taken to curb the problem of obesity among adolescents. Public health interventions at the individual and policy-making levels need to be instigated at the earliest, to tackle this problem in the country.