Plasma FA composition is associated with weight status in healthy adolescents. High intake of long-chain PUFAs, especially n-3 PUFAs, may protect obese subjects against MS and low-grade inflammation as early as adolescence.

OBJECTIVE:To evaluate the 6-month impact of a physical activity (PA) multilevel intervention on activity patterns and psychological predictors of PA among adolescents. The intervention was directed at changing knowledge and attitudes and at providing social support and environmental conditions that encourage PA of adolescents inside and outside school. SUBJECTS AND DESIGN: Randomised, controlled ongoing field trial (ICAPS) in middle-school's first-level adolescents from eight schools selected in the department of the Bas-Rhin (Eastern France) with a cohort of 954 adolescents (92% of the eligible students) initially aged 11.770.6 y. The 6-month changes in participation in leisure organised PA (LOPA), high sedentary (SED) behaviour (43h/day), self-efficacy (SELF) and intention (INTENT) towards PA were analysed after controlling for baseline measures and different covariables (age, overweight, socioprofessional occupation), taking into account the cluster randomisation design. RESULTS: The proportion of intervention adolescents not engaged in organised PA was reduced by 50% whereas it was unchanged among control students. After adjustment for baseline covariables, LOPA participation significantly increased among the intervention adolescents (odds ratio (95% confidence interval) (OR) ¼ 3.38 (1.42-8.05) in girls; 1.73 (1.12-2.66) in boys), while high SED was reduced (OR ¼ 0.54 (0.38-0.77) in girls; 0.52 (0.35-0.76) in boys). The intervention improved SELF in girls, whatever their baseline LOPA (Po10 À4 ) and INTENT in girls with no baseline LOPA (P ¼ 0.04). SELF tended to improve in boys with no baseline LOPA, without reaching statistical significance. When included in the regression, follow-up LOPA was associated with improvement of SELF in girls (P ¼ 0.02) and of INTENT in girls with no baseline PA (Po0.02). The intervention effect was then attenuated. CONCLUSION: After 6 months of intervention, ICAPS was associated with a significant improvement of activity patterns and psychological predictors, indicating a promising approach for modifying the long-term PA level of adolescents.

BACKGROUND AND OBJECTIVE: Waist circumference (W) has been shown to be a good predictor of cardiovascular risk. The aim of this study was to investigate whether physical activity (PA) is related to W in adolescents as previously shown in adults. DESIGN AND SUBJECTS: Cross-sectional population-based survey of 2714 12-y-old adolescents from the eastern part of France. MEASUREMENTS: Body mass index (BMI) and W were measured. Structured PA, active commuting to and from school and sedentary activities (SED), for example television viewing, computer/video games and reading and different potential confounders (dietary habits, parental overweight, family annual income tax and educational level) were assessed by a questionnaire. RESULTS: The adolescents had a mean BMI of 19.073.4 kg/m 2 , and 20.2% of them were overweight, with no gender difference. Boys had a greater W than girls (67.679.1 vs 65.778.9 cm, Po0.0001). In all, 42% of the girls and 25% of the boys did not practice any structured PA outside school and less than 40% of the adolescents commuted actively to school more than 20 min/day. About one-third of the adolescents devoted more than 2 h/day to SED. In univariate analyses, BMI was negatively associated with structured PA but significantly only for girls (Po0.01) and positively associated with SED for both genders (Po0.0001 for girls, Po0.01 for boys). W was negatively associated with structured PA and positively associated with SED both in girls (Po0.0001 and P ¼ 0.03, respectively) and boys (Po0.01 and P ¼ 0.08, respectively). Multiple general linear models show that SED is associated with BMI, independently of structured PA, in both genders. On the other hand, structured PA was inversely associated with W, independently of SED. The inverse relation between structured PA and W persisted after additional adjustment on BMI, with a greater effect of PA for the adolescents with higher BMI. CONCLUSIONS: In 12-y-old adolescents, structured PA is inversely associated with W, an indicator of total adiposity but also more specifically of abdominal fat. This suggests that PA may have a beneficial effect on youth metabolic and cardiovascular risks, in particular in the presence of overweight.

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This study indicates that, as in other industrialised countries, much overweight and obesity are present in 12-year-old French adolescents. It suggests the existence of an influence of socio-economic factors with a predominant effect of the mother's educational level rather than the financial resources.