A socio-ecological approach promoting physical activity and limiting sedentary behavior in adolescence showed weight benefits maintained 2.5 years after intervention cessation.

BACKGROUND: Obesity in youth remains a major public health issue. Yet no effective long-term preventive strategy exists. We previously showed that a school-based socio-ecological approach targeting behavior and social/environmental influences on physical activity (PA) prevented 4-year excessive weight gain in 12-year olds. In this study, we investigated if this efficacy persists 30 months after intervention cessation. METHODS AND FINDINGS: The program targeted students, family, school and the living environment to promote/support PA and prevent sedentary behavior (SB). A total of 732 students from eight randomized middle schools completed the 4-year trial. At the 30-month post-trial follow-up, body mass index (BMI), fat mass index (FMI), leisure PA (LPA), home/school/workplace active commuting, TV/video time (TVT), and attitudes toward PA were measured in 531 adolescents. The beneficial effects of the intervention on the excess BMI increase (+0.01 vs +0.34 kg m(-2) in the intervention and control groups, respectively) and on the overweight incidence in initially non-overweight students (4.3% vs 8.6%; odds ratio=0.48 (95% confidence interval: 0.23-1.01)) were maintained at the post-trial follow-up. LPA was not maintained at the level achieved during the trial. However, we still observed a prevention of the age-related decrease of the adolescents' percentage reporting regular LPA (-14.4% vs -26.5%) and a higher intention to exercise in the intervention group. The intervention promoted lower TVT (-14.0 vs +13.6 min per day) and higher active commuting changes (+11.7% vs -4.8%). Trends in higher BMI reduction in students with high initial TVT and in the least wealthy group were noted. TVT changes throughout the follow-up predicted excess BMI and FMI changes. CONCLUSIONS: Long-term multilevel approach targeting PA and SB prevents excessive weight gain up to 30 months after intervention cessation. The efficacy may be higher in the most sedentary and least wealthy adolescents. Healthy PA-related behavior inducing long-lasting weight effects can be promoted in youth providing that an ecological approach is introduced in the prevention strategy.

Successful overweight prevention in adolescents by increasing physical activity: a 4-year randomized controlled intervention.

BACKGROUND: Population-based studies directed at promoting physical activity in youth have shown limited success in obesity prevention. OBJECTIVE: To assess whether an intervention integrating environmental changes to induce sustained changes in physical activity, prevents overweight in adolescents. DESIGN: Four-year randomized trial started in 2002 in eight middle schools of Eastern France. The intervention, randomized at school level, was designed to promote physical activity by changing attitudes through debates and attractive activities, and by providing social support and environmental changes encouraging physical activity. SUBJECTS: Nine hundred and fifty four 12-year-old six-graders. MEASUREMENTS: Body mass index (BMI), body composition, physical activity by questionnaire, plasma lipids and glucose, insulin resistance. RESULTS: Intervention students had a lower increase in BMI (P=0.01) and age- and gender-adjusted BMI (P<0.02) over time than controls. The differences across groups of the age- and gender-adjusted BMI changes (95% confidence interval (CI)) were -0.29 (-0.51; -0.07) kg/m2 at 3 years, -0.25 (-0.51; 0.01) kg/m2 at 4 years. An interaction with baseline weight status was noted. The intervention had a significant effect throughout the study in initially non-overweight adolescents (-0.36 (-0.60;-0.11) kg/m2 for adjusted BMI at 4 years), corresponding to a lower increase in fat mass index (P<0.001). In initially overweight adolescents, the differences observed across groups at 2 years (-0.40 (-0.94; 0.13) kg/m2 for adjusted BMI) did not persist over time. At 4 years, 4.2% of the initially non-overweight adolescents were overweight in the intervention schools, 9.8% in the controls (odds ratio=0.41 (0.22; 0.75); P<0.01). Independent of initial weight status, compared with controls, intervention adolescents had an increase in supervised physical activity (P<0.0001), a decrease of TV/video viewing (P<0.01) and an increase of high-density cholesterol concentrations (P<0.0001). CONCLUSION: Enhancing physical activity with a multilevel program prevents excessive weight gain in non-overweight adolescents. Our study provides evidence that prevention of obesity in youth is feasible.

Adiponectin is associated with lipid profile and insulin sensitivity in French adolescents.

AIM: The favourable relationship of adiponectin with the metabolic profile demonstrated in adults has been less studied in youths. The aim of this study was to examine cross-sectional and longitudinal associations between adiponectin and various metabolic risk factors in 12-year-old adolescents. METHODS: Subjects were participants in a randomized controlled study to promote physical activity (PA). Cross-sectional associations were assessed at entry in 2002 among 647 PA-exposed and control first-level students (49% male, 11.6+/-0.6 years of age). Longitudinal analyses involved 288 control students surveyed in 2002 and 2004. Baseline measurements included fasting serum adiponectin and anthropometric indices (body mass, waist size, body fat [BF] by bioimpedance), insulin concentration, homeostasis model assessment (HOMA), high-density lipoprotein (HDL) cholesterol, triglycerides (TG), soluble TNF-alpha receptor 1 (sTNF-alpha R1) and high-sensitivity C-reactive protein. Analyses were performed with generalized linear mixed-effects models, taking into account correlations among adolescents in the same school. RESULTS: Cross-sectionally, plasma adiponectin was inversely associated with obesity indices, especially waist size (P<10(-2)), HOMA (P<0.03), insulin (P<0.04), TG (P<10(-2)) and sTNF-alpha R1 (P<0.05), and positively related to HDL cholesterol (P<10(-4)), after adjusting for age, gender, sexual maturity, sports participation and adiposity when relevant. Longitudinally, a higher baseline adiponectin level was associated with a more favourable two-year change in TG (P<0.05), even after accounting for baseline TG, and two-year BF and insulin changes. CONCLUSION: The findings of this study suggest a favourable relationship between adiponectin and both metabolic profile and subsequent changes in TG level in young adolescents.

ICAPS: a multilevel program to improve physical activity in adolescents.

OBJECTIVES: ICAPS (Intervention Centred on Adolescents' Physical activity and Sedentary behaviour) is aimed at preventing excessive weight gain and cardiovascular risk in adolescents by promoting physical activity (PA) with an emphasis on recreational and daily-life PA, with a lifelong perspective. DESIGN: Randomized study designed to last for four years. Study cohort constituted of 954 first-level students (91% of eligible pupils), aged 11.7 +/- 0.6 y (mean +/- SD) from four pairs of schools randomly selected in eastern France, after sociogeographical stratification. In each pair, intervention status was randomised at school-level. The program, not limited to school settings, involves multiple partners with three objectives: 1) changing attitudes through debates and access to attractive activities during breaks and after-school hours, 2) encouraging social support, 3) providing environmental conditions that enable PA. Adapted times and places, open participation, emphasis on fun, meeting with others and absence of competitive aspects are used to reduce usual barriers to PA. Accessibility and safety are permanent concerns. RESULTS: Prevalence of overweight was 23.7%. High participation rates were attained (50% participated in at least one weekly activity). At six-month, the proportion of intervention adolescents not performing supervised PA out of academic PA was reduced by half (36% to 17% vs 42% to 42% in controls P < 10-4); the proportion of those spending > 3 h/day in sedentary occupations decreased (34% to 28% vs 27% to 36%; P < 10-4). CONCLUSION: These data demonstrate the feasibility of implementing a multilevel PA intervention program in adolescents. Six-month results document increased PA and decreased sedentary behaviour.

Parent-child physical activity relationships in 12-year old French students do not depend on family socioeconomic status.

OBJECTIVES: Regular physical activity (PA) in young needs to be promoted to prevent obesity and subsequent diabetes. Influences of parental PA on adolescents' activity level have been studied with discordant results and the effect of socioeconomic status (SES) on these relationships is not clarified. METHODS: Cross-sectional population-based survey of about 3000 12-year old French students and their parents. Familial associations were assessed with logistic regression models taking into account SES and children's and parents' corpulence. Sport involvement and sedentary behaviors were assessed by standardized questionnaires filled out separately by children and parents, the latter also reporting their educational data and family income tax. RESULTS: Participation in structured PA outside school was higher for boys (74%) than for girls (58%, p<10-5) and a high sedentary behavior (watching television, playing computer/video games and reading > or =2h/day) was observed in one-third of the sample, both in boys and in girls. Children were more likely to participate in structured PA outside school when both parents practiced sport as compared to neither parent practicing it, with an odd ratio OR (95%CI) of 1.97 (1.4-2.8) for boys and 1.56 (1.2-2.1) for girls. Familial associations of inactivity were significant for boys only. A greater percentage of adolescents had a high level of sedentary behavior when both parents versus no parents watched television > 2h/day (OR 1.95 (1.52.6)). Parent-child physical activity relationships were not modified by the family SES or the children's or parents' weight status. CONCLUSION: Parental involvement in sport is an important correlate of a young adolescent's participation in structured PA outside school, whatever the family SES or corpulence of the family members.

Habitual physical activity, physical fitness and heart rate variability in preadolescents.

The amount and type of physical activity (PA) appropriate in youth for optimal health is still being discussed. The purpose of this study on 12-year-old preadolescents is to evaluate the association of two PA patterns, corresponding to different exercise intensities, with some health-related indexes. PA was evaluated by triaxial accelerometry in 67 student subjects, who were successively classified according to 1) their usual participation or not in moderately intense (> 4 metabolic equivalents, METs) activities (either in daily life or in leisure activities) for at least 210 min a week (4 M (210)); and 2) the habitual practice or not of more intense activities (> 6 METs) for at least 60 min a week (6 M (60)). Health-related indexes consisted of cardiopulmonary (maximum oxygen uptake, V.O 2max), muscular (lower limb strength) fitness parameters and vagal-related indexes of heart rate (HR) variability (HRV), such as the HF/(LF+HF) ratio (where HF and LF stand for high and low frequency power). HR was recorded in the supine position after 15 min of quiet rest, and HRV indexes were calculated in 5-min segments. Energy expenditure due to PA was not significantly associated with any health-related index. Reaching 4 M (210) was associated with both higher estimated V.O 2max (p < 0.05) and higher muscular strength indexes (p < 0.05) but not with enhanced HRV indexes. Subjects who reached 6 M (60) had higher estimated V.O2max (p < 0.05) and higher HF/(LF+HF) (p < 0.05). Our results show that regular moderately intense activities are sufficient to influence physical fitness but suggest that more intense activities are necessary to observe more favorable HRV vagal-related indexes.

Relationships of physical activity with metabolic syndrome features and low-grade inflammation in adolescents.

AIMS/HYPOTHESIS: Physical activity has beneficial effects on symptoms of the metabolic syndrome and low-grade inflammation in adults. These associations have rarely been studied in adolescents. Moreover, it has not been established whether they depend on adiposity, fat localisation and adipokines. SUBJECTS, MATERIALS AND METHODS: We used cross-sectional data of 640 12-year-old adolescents participating in the Intervention Centred on Adolescents' Physical Activity and Sedentary Behaviour Study (ICAPS). Weight, height, body fat mass and WHR were measured. Metabolic syndrome components, two inflammatory markers (IL-6 and C-reactive protein), plasma leptin, adiponectin and soluble TNF-alpha receptor 1 (sTNF-alpha R1) were determined. Insulin resistance was estimated by homeostasis model assessment (HOMA) and energy expenditure due to organised leisure-time physical activity (PAE) assessed by questionnaire. RESULTS: The metabolic syndrome was present in 5.8% of the adolescents. After adjustment for sex, sexual maturity and socio-economic status, a beneficial relationship between PAE and all metabolic syndrome features was found, but only the associations with HOMA and IL-6 were independent of body fat mass and WHR. Adjusted means from the lowest to the highest tertile of PAE were 1.99, 1.80 and 1.78 for HOMA (p=0.04), and 0.88, 0.69 and 0.70 pg/ml for IL-6 (p=0.02). PAE was inversely associated with leptin, independently of body fat mass and WHR (p<10(-2)), but not with adiponectin or sTNF-alpha R1. Further adjustment for adipokines did not change the relationships of PAE with HOMA and IL-6. CONCLUSIONS/INTERPRETATION: In adolescents, physical activity is inversely related to HOMA and IL-6, independently of adiposity and fat localisation. These relationships are not accounted for by adipokines.

Physical activity is inversely related to waist circumference in 12-y-old French 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 2,714 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 19.0+/-3.4 kg/m2, and 20.2% of them were overweight, with no gender difference. Boys had a greater W than girls (67.6+/-9.1 vs 65.7+/-8.9 cm, P<0.0001). 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 (P<0.01) and positively associated with SED for both genders (P<0.0001 for girls, P<0.01 for boys). W was negatively associated with structured PA and positively associated with SED both in girls (P<0.0001 and P=0.03, respectively) and boys (P<0.01 and P=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..

Prevalence and sociodemographic determinants of overweight in young French adolescents.

BACKGROUND: The prevalence of overweight in adults and in children is increasing in most industrialised countries. Our purpose is to estimate the prevalence of overweight and obesity in a population of 12-year-old French adolescents and to analyse its association with different sociodemographic factors. METHODS: A cross-sectional study was conducted in 2001 on a representative sample of sixth-grade adolescents (mean age 12.1 +/- 0.6 years) living in the Department of the Bas-Rhin (Eastern part of France). Height and weight were measured in 4326 adolescents. Overweight and obesity were defined as recommended by the International Obesity Task Force. Sociodemographic data were obtained for 3436 adolescents. RESULTS: The prevalence of overweight was 22.7% (17.5% of moderate overweight and 5.2% of obesity) and it was not different by gender or by size of the commune of residence. Overweight was more frequent in low economic zones (p < 10(-4) in girls, p < 10(-2) in boys) and in public schools than in private schools (p < 10(-3) in girls). The prevalence of overweight was inversely associated with family income tax (p < 10(-3) in girls, p = 0.012 in boys), mother's (p = 10(-4) in girls, p = 10(-3) in boys) and father's (p = 0.001 in girls, p = 0.004 in boys) educational level. Multiple logistic regression analysis indicated an independent association of being overweight with low family income tax (p = 0.2195) and poor mother's educational level (p = 0.0193). CONCLUSIONS: 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.

Intervention centred on adolescents' physical activity and sedentary behaviour (ICAPS): concept and 6-month results.

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 11.7+/-0.6 y. The 6-month changes in participation in leisure organised PA (LOPA), high sedentary (SED) behaviour (>3 h/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)=3.38 (1.42-8.05) in girls; 1.73 (1.12-2.66) in boys), while high SED was reduced (OR=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 (P<10(-4)) and INTENT in girls with no baseline LOPA (P=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=0.02) and of INTENT in girls with no baseline PA (P<0.02). 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.