Carine Platat

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.

Association Between Television in Bedroom and Adiposity Throughout Adolescence

Objective: The objective was to determine if having a television (TV) in the bedroom is associated with physical activity (PA), TV/video viewing, and adiposity throughout adolescence.

Activity energy expenditure is a major determinant of dietary fat oxidation and trafficking, but the deleterious effect of detraining is more marked than the beneficial effect of training at current recommendations

BACKGROUND Previous studies suggested that physical activity energy expenditure (AEE) is a major determinant of dietary fat oxidation, which is a central component of fat metabolism and body weight regulation. OBJECTIVE We tested this hypothesis by investigating the effect of contrasted physical activity levels on dietary saturated and monounsaturated fatty acid oxidation in relation to insulin sensitivity while controlling energy balance. DESIGN Sedentary lean men (n = 10) trained for 2 mo according to the current guidelines on physical activity, and active lean men (n = 9) detrained for 1 mo by reducing structured and spontaneous activity. Dietary [d31]palmitate and [1-¹³C]oleate oxidation and incorporation into triglyceride-rich lipoproteins and nonesterified fatty acid, AEE, and muscle markers were studied before and after interventions. RESULTS Training increased palmitate and oleate oxidation by 27% and 20%, respectively, whereas detraining reduced them by 31% and 13%, respectively (P < 0.05 for all). Changes in AEE were positively correlated with changes in oleate (R² = 0.62, P < 0.001) and palmitate (R² = 0.66, P < 0.0001) oxidation. The d31-palmitate appearance in nonesterified fatty acid and very-low-density lipoprotein pools was negatively associated with changes in fatty acid translocase CD36 (R² = 0.30), fatty acid transport protein 1 (R² = 0.24), and AcylCoA synthetase long chain family member 1 (ACSL1) (R² = 0.25) expressions and with changes in fatty acid binding protein expression (R² = 0.33). The d31-palmitate oxidation correlated with changes in ACSL1 (R² = 0.39) and carnitine palmitoyltransferase 1 (R² = 0.30) expressions (P < 0.05 for all). Similar relations were observed with oleate. Insulin response was associated with AEE (R² = 0.34, P = 0.02) and oleate (R² = 0.52, P < 0.01) and palmitate (R² = 0.62, P < 001) oxidation. CONCLUSION Training and detraining modified the oxidation of the 2 most common dietary fats, likely through a better trafficking and uptake by the muscle, which was negatively associated with whole-body insulin sensitivity.

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.