OBJECTIVE: To assess the association of physical activity, television program viewing and other forms of video viewing with the prevalence of obesity among school children. DESIGN: Cross-sectional study. SUBJECTS: 712 children, 9 ± 16 y old, from a low-and a middle-income town in the Mexico City area. MEASUREMENTS: Children completed a self administered questionnaire to assess time spent in physical activity and television viewing, and diet. Height weight and triceps skinfolds were measured. The outcome variable was obesity, and the covariates were hours of television programs and other video viewing, physical activity, energy intake, percentage of energy from fat, town of location of school, age, gender and perception of mother's weight status. RESULTS: Among 461 children with complete information, 24% were classi®ed as obese. Children reported an average of 4.1 AE 2.2 had watching television (2.4 AE 1.5 had for TV programs and 1.7 AE 1.5 had for video cassette recorder (VCR) or videogames), and 1.8 AE 1.3 had in moderate and vigorous physical activities. Odds ratios (OR) of obesity were 12% higher for each hour of television program viewing per day (OR 1.12, 95% con®dence interval (CI) 1.02, ± 1.22), and 10% lower for each hour of moderateavigorous physical activity per day (OR 0.90, 95% CI 0.83 ± 0:98), controlling for age, gender, town and perception of mother's weight status. Children in the middle-income town had higher adjusted odds of obesity (OR 2.58, 95% CI 1.47 ± 4.54). CONCLUSION: Physical activity and television viewing, but not VCRavideogames use, were related to obesity prevalence in Mexican children 9 ± 16 y old.

Objective: To assess the reproducibility and validity of a semiquantitative food frequency questionnaire (FFQ) to classify children and adolescents in terms of daily servings of fruits and vegetables and intake of calories, protein, fat, carbohydrate, dietary fibre, vitamin C, phosphorous, calcium and iron. Design: FFQs were collected in the autumn of 1993 and 1994. Four 24-hour diet recalls were collected during the same 1-year period and their mean was compared to the FFQ diet estimates. Setting: Low income, inner-city state schools. Subjects: A sample of 109 inner-city fourth to seventh grade students. Results: The 1-year reproducibility of the FFQ, assessed with Spearman correlations, was lower among the fourth and fifth (range: r ¼ −0.26 to 0.40) than the sixth and seventh grade students (range: r ¼ 0.18-0.47). After adjusting for day-to-day variation in dietary intake, for most nutrients and foods the correlations between the FFQ and the 24-hour recalls remained greater among the junior high school students (fourth to fifth grade range: r ¼ 0.0-0.42; sixth to seventh grade range: r ¼ 0.07-0.76). Conclusions: Inner-city sixth and seventh grade students demonstrated the ability to provide valid estimates of intake of calories, carbohydrate, calcium, phosphorous, iron and vitamin C over the past year. However, children in the fourth and fifth grades experienced some difficulty in completing the FFQ. Our results suggest that, before using this instrument with fourth and fifth grade children, investigators should assess whether study participants can think abstractly and are familiar with the concept of 'average intake'.

Increases in screen time were associated with increased consumption of foods and beverages of low nutritional quality and decreased consumption of fruit and vegetables. Our results caution against excessive use of screen media, especially television, in youth.

IntdudionAlthough studies have explored the frequency' and determinants2 of children's participation in physical activities, racial/ethnic and age differences (elementaly to high school) in activity levels have not been studied; also, the relationship between physical activity, sedentary behavior, and the prevalence of obesity in different racial/ethnic and age groups has not been examined. This study explored race-, ethnicity-, and age-related differences in activity, inactivity, and obesity among a multiracial sample of girls in grades 5 through 12 living in a low-tomedium income northeastem town. MeodsA school-based survey was administered from February through May 1991 to 552 girls residing in Lynn, Mass. The ethnic composition ofthe study population (64.3% White, 15.4% Black, 11.2% Hispanic, 4.3% Asian, and 4.7% other/mixed) was representative of the school district. Elementaiy schools (grades 5 and 6), junior high schools (grades 7 and 8), and high schools (grades 9 through 12) contnbuted 29.5%, 37.1%, and 33.3%, respectively, of the study population. After active parental consent was obtained and dropouts and absentees were excluded, the estimated response rate among students who were eligible to receive the questionnaire was 78%.Physical activity was self-reported on the Godin-Shepard Physical Activity Survey,3 which has good 2-week test-retest reliability and construct validity among children.4 The survey was modified by developing Height and weight were self-reported. Obesity was defined by age-and sex-appropriate reference data of body mass index (kg/i2) at the 85th percentile.5 Sedentary behavior or inactivitywas assessed by number of hours of television viewed per day; six closed-ended categories (ranging from less than 1 hour to 9.5 hours per day) were used in these assessments.Statistical Analysis Software6 was used in conducting statistical analyses. Age, race, and age-adjusted body mass index were controlled for in these analyses. Indicator variables were used for racial/ethnic and age groups, with White and high school as the referent groups.

The relationship of obesity to environmental factors such as season, region, and population density was examined in children studied during cycle II of the National Health Examination Survey. This survey selected 7119 children aged 6 to 11 yr old from a representative noninstitutionalized sample of the United States population. The prevalence of obesity (triceps skinfold more than the 85th percentile) was significantly more in the Northeast and Midwest than in the West and significantly more in large metropolitan areas than in areas with lower population densities. The prevalence of obesity was generally lowest in the summer and highest in the fall or winter. Each environmental variable was associated with 2- to 3-fold variations in the prevalence of obesity. The effect of region, population density, and season appeared independent of race and socioeconomic status. Similar relationships were found for superobesity (triceps skinfold more than the 95th percentile). These results emphasize that environmental variables significantly affect the prevalence of obesity and could help account for the wide variations in prevalence that have been previously published. Understanding the mechanisms by which the environment affects childhood obesity may improve the effectiveness of community level interventions.