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Background Interventions promoting healthy behaviors such as physical activity are effective to prevent overweight and obesity among adolescents. Following such interventions, body satisfaction change could be discrepant with weight change (e.g. less body satisfaction while having lost weight), and decrease sustainability of behaviors in the long-term. This study aimed to describe the discrepancy between body satisfaction change and weight change among adolescents following a 2-year school-based intervention, and to identify associated sociodemographic factors. Methods Adolescents from the 2-year school-based ‘Promotion de l'Alimentation et de l'Activité Physique’ study conducted in northeastern France from 2006 to 2009 were included. Body satisfaction change was assessed using a self-administered questionnaire at the end of the study. Weight change was measured by the difference of body mass index z-score at end and start of the study. Discrepancy between body satisfaction change and weight change was described with cross-tabulations and weighted Cohen's kappa. Sociodemographic factors associated with discrepancy were determined by multivariate logistic regression models. Results Among the 3279 adolescents included (mean ± standard deviation age= 15.2±0.6 years), the proportion of discrepancy between body satisfaction change and weight change was 74.8% (pessimism= 41.6%; optimism= 33.2%). The weighted Cohen's kappa indicated high discrepancy (?= 0.09; 95% confidence interval [0.07; 0.11]). The likelihood of discrepancy, especially pessimism was higher in boys than in girls (odds ratio= 1.44, 95% confidence interval [1.19; 1.74], p= .0002), and higher in adolescents with high socioeconomic status than in those with low socioeconomic status (odds ratio= 1.82; 95% confidence interval [1.20; 2.74], p= .004) Conclusions Discrepancy between body satisfaction change and weight change was high among school-aged adolescents with increased likelihood for boys and adolescents with high socioeconomic status. Body satisfaction change should be considered in overweight and obesity prevention interventions alongside body weight change, and could be used as an indicator of long-term behavior maintenance.

Background If boys and girls are known to have different levels of quality of life (HRQoL), less is known about behavioural factors such as physical activity (PA), sedentary behaviour (SB) that can explain it. We aimed to analyse the mediation effect of PA and SB on the association of sex and HRQoL among adolescents. Methods 2448 adolescents (1378, 56.3% of Girls) from the PRALIMAP trial with 2-year follow-up were included. HRQoL (physical, mental, social and general dimension scores; range 0-100), PA (walking, moderate vigorous and total) and SB (sitting time) were assessed using the Duke Health profile and the IPAQ questionnaires, respectively. The 2-year mean PA and SB were calculated and categorized into high or low PA (? 1hour/day) or SB (2 hours/day out of school). We conducted a mediation analysis to investigate the causal mechanism of gender (reference=Girls) on HRQoL through PA and SB by estimating total effect (TE), natural direct effect (NDE), natural indirect effects (NIE) as well as proportion mediated (PM: proportion of sex-HRQoL relationship mediated by PA or SB). Results The direct relationship of gender and HRQoL (NDE) was significant whatever the HRQoL dimension. When using vigorous PA as mediator, PM was estimated at 13.7% (TE:11.0 [9.5 to 12.5]; NIE:1.5[0.9 to 2.1]), 19.4% (TE: 12.3 [10.6 to 14.1]; NIE: 2.4 [1.6 to 3.1]), 70.0% (TE:4.6 [3.1 to 6.2] ; NIE: 3.3 [2.5 to 4.0]) and 25.6% (TE: 9.3 [8.1 to 10.5]; NIE:2.4 [1.8 to 2.9]) for physical, mental, social and general HRQoL, respectively. Similar but less important mediation effect was observed for moderate and walking PA. For Total PA, PM was estimated 7.0%, 8.7%, 47.4% and 14.7% for physical, mental, social and general HRQoL while for SB, the mediation was inverse and less important (PM: -1.5%, -1.4%, -2.0% and -1.5% for physical, mental, social and general HRQoL respectively). Conclusion HRQoL is significantly higher in boys compared to girls among adolescents and this difference is shown to be partially mediated by differences in PA practice, especially vigorous PA. Additionally to the impact of adolescent PA in preventing non-communicable diseases in adulthood, it can also enhance their well-being.

Objective:To investigate clustering of risk behaviours in adolescents with excess weight.Design:Cross-sectional analysis of baseline data from the PRALIMAP-INÈS trial. Information on food frequency consumption (fruit, vegetables, sugary products and beverages), physical activity, sedentary behaviour (week and weekend days), smoking and alcohol consumption (current frequency and intoxication episodes) and socio-demographic data was collected using self-reported questionnaires. Behavioural risk factors were entered as categorical variables in a two-step clustering procedure: multiple correspondence analysis followed by hierarchical clustering. Associations between cluster membership and socio-demographic variables were investigated using multivariable multinomial logistic regression.Setting:French PRALIMAP-INÈS trial.Participants:Adolescents with excess weight.Results:A total of 1391 participants (13–18 years old, 58·2 % female) were included in the analysis, which resulted in the identification of four groups of participants, including, respectively, 543 (39·0 %), 373 (26·8 %), 246 (17·7 %) and 229 (16·5 %) participants. Clusters 1 and 4 showed associations of rather healthy behaviours (high physical activity and low consumption of sugary products; high consumption of fruit and vegetables, respectively), while clusters 2 and 3 showed associations of rather unhealthy behaviours (high sedentary behaviour and low consumption of fruit and vegetables; smoking and alcohol consumption, respectively). Both social status and family structure were associated with cluster membership.Conclusions:Risk behaviour patterns in adolescents with excess weight were clustered in both healthier and less healthy ways, with a complex interplay with socio-demographic factors.

Background: This study aimed to quantify the 2-year mediating effects of physical activity (PA) and eating behavior (EB) on socioeconomic and sex inequalities in quality of life (QoL) among French adolescents. Methods: Adolescents from a 2-year school-based trial were included. PA and EB were assessed at baseline, 1 year, and 2 years using the International Physical Activity Questionnaire and an eating habits questionnaire, respectively. QoL was measured at 2 years using the Duke Health Profile questionnaire. The mediating effect of adherence to PA and EB guidelines in the associations between socioeconomic status or sex and QoL was analyzed with a counterfactual method. Results: Among the 3562 included adolescents (mean age, 15.2 [0.6] y), being a boy and having a high socioeconomic status was associated with high QoL. Differences in QoL by socioeconomic status were mediated by adherence to guidelines for PA (up to 10.2%) and EB (up to 8.8%), and differences in QoL by sex were predominantly mediated by adherence to guidelines for PA (up to 163.8%). Conclusions: Policies, programs, and interventions designed to reduce socioeconomic and sex inequalities in QoL among adolescents could use PA and EB as leverage.

A laminar-flow tubular crystallizer was used for seedless continuous flow crystallization of an active pharmaceutical ingredient, namely, Brivaracetam, which has a polymorphic behavior: rod-shaped crystals and a pseudo-polymorphic solvated, needle-like crystal. The combination of fast cooling at 20 °C/s and high supersaturation values between 4 and 11 resulted in the discrimination of nucleation and growth of only the desired crystalline form even though its solubility curve is very close to the one of the undesired needle shape. Crystal nucleation and the start of crystal growth occur inside the tubular crystallizer; high flow rates prevent clogging of the crystallizer. Further crystal growth may be, if desired, stopped via immediate filtration. In this way, an industrially applicable continuous crystallizer is proposed. It is also demonstrated that the presence of restrictions in the tubing drastically increases the nucleation rate. A literature survey points out that induced turbulence can occur under ...

International audience; Social differences in prevalence of overweight and obesity among adolescents, known as the weight social gradient, could be explained by differences in behaviours between social classes. This study examined the respective association of physical activity (PA), sedentary behaviour (SB) and weight status with adolescents' socioeconomic status. We used cross-sectional data for 1935 adolescents (13-18 years old) with overweight or obesity who participated in the PRALIMAP-INÉS (PRomotion de l'ALImentation et de l'Activité Physique - INÉgalités de Santé) trial conducted in northeastern France between 2012 and 2015. Adolescents completed the International Physical Activity Questionnaire for PA and SB and the Family Affluence Scale for socioeconomic status. Weight status was assessed by the body mass index (BMI) and BMI z-score. Social gradient of weight status, PA and SB were described according to the Family Affluence Scale (slopes) and evidenced by the linear trend test (p). Adolescents' socioeconomic status was positively associated with PA practice (frequency, vigorous PA and leisure-time PA), but there was no association with their SB. The results confirmed a significant weight social gradient: BMI (β = 0.37, p

International audience; BACKGROUND: A high prevalence of overweight/obesity among low socioeconomic status adolescents contributes to health inequalities. However, evidence-based interventions for reducing social inequalities in adolescent weight are lacking. We aimed to investigate whether strengthened care management for adolescents with low socioeconomic status has an equivalent effect in reducing overweight as standard care management in adolescents with high status.METHODS: PRALIMAP-INÈS was a multicentre trial including 35 state-run high and middle schools in the north-eastern France. A population-based sample of 1639 adolescents aged 13-18 years with screened and clinically confirmed overweight/obesity were proposed for inclusion and divided into two groups by the Family Affluence Scale score: advantaged (score > 5), receiving standard care management (A.S) and less-advantaged randomly assigned to two groups (1:2 ratio): standard care management (LA.S) and standard and strengthened care management (LA.S.S). Interventions were based on the proportionate universalism principle: universal standard care for all groups and proportionate care for the LA.S.S group. Main outcome was body mass index z-score (BMIz) assessed before and 1 year after inclusion.RESULTS: A total of 1419 adolescents were included and 1143 followed up at 1 year: 649 in A.S, 158 in LA.S and 336 in LA.S.S groups. BMIz decreased significantly for boys (-0.11 [95% CI, -0.13 to -0.08]; p

Initial participation in PRALIMAP-INÉS group activities was high among disadvantaged teenagers with financial difficulties, but it was more difficult to maintain their participation throughout the programme. Identification of factors that can maintain participation is a major challenge for continuity of the programme./ce:para.

Background:explaining why and how overweight prevention programs were effective was a real need; especially the potential role of physical activity (PA) and sedentary behavior (SB) should be highlighted. This study aimed to evaluate the 2-year effectiveness of a screening and care strategy in adolescents’ weight reduction with regards to PA and SB change.Methods:1745 adolescents aged 15.1 years from PRALIMAP trial was included (n = 840 for screening and care group and n = 905 for control group). PA and SB time (international physical activity questionnaire: IPAQ), body mass index (BMI), and BMI z-score were assessed at inclusion and after 2-year intervention. Hierarchical mixed models were applied.Results:Compared with the control group, screening and care strategy was associated with an increase in global PA (58 min/week), a moderate PA (43 min/week), the adherence to the French PA guidelines (OR = 1.3), and a decrease in SB (−198 min/week). The 2-year weight change decreased when adjusted for PA and SB suggesting that the effect of screening and care strategy was partly mediated by PA and SB.Conclusion:Screening and care intervention seemed to be effective in increasing PA and decreasing SB. The induced PA and SB modifications contributed to the observed weight change.

The aim of this study was to assess the associ- ation between smoking, food consumption, and antioxidant vita- min intake and plasma indexes of oxidative stress and antioxi- dant defenses in French adults. Food and nutrient intakes of 459 healthy men aged 23-57 y were estimated by the diet history method and analyzed by smoking status. Plasma a-tocopherol, ascorbic acid, and carotenoids were measured as antioxidants and malondialdehyde, protein Schiff bases, and autoantibodies against malondialdehyde-protein adducts as oxidative stress indexes. Smokers ate less fruit and vegetables than nonsmokers, leading to lower vitamin E, vitamin C, and carotene intakes, even after adjustment for age, education, and marital status. Unlike vitamin E, plasma ascorbic acid and b-carotene concentrations were reduced in smokers compared with nonsmokers and were inversely related to cigarette consumption. This difference remained significant after adjustment for alcohol and dietary intakes. Among the measured oxidative stress indexes, only Schiff base concentration was positively related to the number of cigarettes smoked. In our sample of French men, smoking had an adverse effect on antioxidant status; vitamin intakes were reduced in smokers and plasma antioxidant indexes were altered independently of dietary intakes. As in other countries, in France smokers require particular attention in terms of public health intervention. Am J Clin Nutr 1998;67:231-9.

Segregation analysis using a regressive model with age- and sex-dependent effects was applied to family data of weight, fat mass (FM) and fat-free mass (FFM) to investigate the major gene hypothesis. The sample consisted of 220 nuclear families from the 'Stanislas Cohort' who volunteered for a free health examination (n = 913). FM and FFM were assessed by bioelectrical impedance. The data were adjusted for height2 and height prior to analysis. The spouse, father-offspring, mother-offspring and sib-sib correlations were: 0.16, 0.18, 0.25 and 0.32 for weight; 0.13, 0.20, 0.23 and 0.28 for FM; 0.18, 0.16, 0.29 and 0.41 for FFM. For the three phenotypes, models specifying a major gene with age- and sex-dependent effects and residual family correlations was better supported than models including only family correlations. For weight, the most parsimonious genetic model was a codominant model with a sex-dependent effect in parents and an age-increasing effect in offspring. For FM, the most parsimonious model was also a codominant model with sex-dependent effects in parents indicating higher effects in women than in men. For FFM, the most parsimonious model was a recessive model with no significant age or sex interaction, although the age interactions paralleled those observed on weight in offspring. For weight and FM, mendelian transmission was rejected. For FFM, the Mendelian and the environmental hypotheses were nearly equally supported and none was rejected when compared to general transmission. Then, evidence for a single major gene could not be inferred for any of the traits. This does not preclude the existence of several genes acting in a more complex way. However, our findings emphasize that weight is a composite phenotype reflecting different components which evolve in distinct ways during life span. For this reason, FM should be highly preferred to weight or BMI for the research of susceptibility genes to obesity.

The biological variation factors for cholesterol in circulating immune complexes (CIC-cholesterol) were studied in 941 unselected supposedly healthy volunteers, ages 4 to 78 years. We found a complex effect of age, including the existence of two peaks of CIC-cholesterol, one in males between 11 and 14 years and in females between 11 and 30 years, and in both sexes another peak between 41 and 60 years, and in both sexes a decrease between 31 and 40 years. By use of multiple regression analysis and after adjustment for age, CIC-cholesterol was positively related to plasma cholesterol concentration and leukocyte count, values being lower in females than in males and among subjects taking anti-inflammatory drugs. In addition, CIC-cholesterol was measured in 76 coronary angiography patients and in 100 supposedly healthy controls, ages 30 to 77 years. We noticed a significant increase (P < or = 0.05) of CIC-cholesterol when patients were affected by coronary stenosis between 20% and 50% (71.8 +/- 52.5 mumol/L vs 46.2 +/- 45.9 mumol/L in controls), but this was less pronounced in those with > 50% of obstruction (58.9 +/- 54.3 mumol/L); however, serum total cholesterol was not modified or even surprisingly slightly decreased in the coronary angiography individuals. Nevertheless, an important overlap of values in controls and patients makes questionable the usefulness of this variable in clinical practice.

Given the increasing prevalence of obesity among youth over the past decade, prevention has become an international public health priority.To evaluate the 2-year effectiveness of three strategies aimed at preventing overweight and obesity among adolescents in a high school setting.PRomotion de l'ALIMentation et de l'Activité Physique (PRALIMAP) is a school-based RCT. Each study high school was assigned to receive or not, over a 2-year period (Grades 10 and 11), each of three prevention strategies according to a 2 × 2 × 2 factorial school randomization. Data were collected in 2006-2009 and analyzed in 2009-2011.A total of 3538 adolescents (aged 15.6±0.7 years at baseline) in 24 public high schools in Lorraine (northeastern France) completed the PRALIMAP trial.The prevention strategies were education (development of nutritional knowledge and skills); environment (creation of a favorable environment by improving availability of "healthy" dietary items and physical activity); and screening and care (detection of overweight/obesity and, if necessary, adapted care management).The main outcome of interest was BMI; BMI z-score and prevalence of overweight/obesity were considered as secondary outcomes.Adolescents who completed the PRALIMAP trial were younger, less often suspected of having eating disorders and depression, and came from a higher socioeconomic class than those who did not. The 2-year change of outcomes was more favorable in the 12 screening and care high schools compared to the no-screening ones: a 0.11 lower increase in BMI (p=0.0303); a 0.04 greater decrease in BMI z-score (p=0.0173); and a 1.71% greater decrease in overweight/obesity prevalence (p=0.0386). Education and environment strategies were not more effective than no strategy intervention.Although the screening and care strategy is an effective way to prevent, at 2 years, overweight and obesity among adolescents in a high school setting, its effects over and above no strategy intervention were small.This study is registered at www.clinicaltrials.govNCT00814554.

Abstract —The relations between left ventricular mass (LVM) with age, gender, body size, and blood pressure were investigated in healthy adults and children from 149 nuclear families. LVM was strongly correlated with overall weight, especially in the children. Genetic analysis indicated that the segregation of LVM was compatible with an additive polygenic model, with a heritability estimate of 34% before adjustment for weight and 28% after adjustment for weight. Genetic and/or familial environmental factors played a strong role in the correlation of LVM and weight; they accounted for all of the correlation between the 2 traits in adults and 59% of the correlation in children. Spouses exhibited a strong correlation in their weight, which suggested that common family environment may contribute to the family correlations and to the observed heritability of the trait. LVM was strongly correlated with blood pressure before adjustment for weight, but this correlation could be attributed to nonfamilial environment rather than genetic factors. After adjustment for weight, the intertrait correlations between LVM and blood pressure were nonsignificant. Thus, adjustment for weight accounts for all common determinants of LVM and blood pressure.

Abstract The main objective of the Stanislas cohort is to study the role and the contribution of genetic and environmental factors to cardiovascular status. We plan: a) to describe the degree of association of a large number of cardiovascular risk indicators with cardiovascular endpoints, b) to evaluate the contribution of genetic and that of environmental factors to this association, c) to follow the evolution of these risk indicators during a period of at least ten years, d) to search for the determinants influencing this evolution. The principal variables studied are: a) to describe the degree of association of a large number of cardiovascular risk indicators with cardiovascular endpoints, b) to evaluate the contribution of genetic and that of environmental factors to this association, c) to follow the evolution of these risk indicators during a period of at least ten years, d) to search for the determinants influencing this evolution. a) blood pressure, cardiac mass, and wall thickness of carotid and femoral arteries, b) obesity and fat mass, c) indicators of lipid metabolism, d) genetic polymorphisms of several cardiovascular risk candidate genes, e) food, tobacco and alcohol consumption, f) consumption of drugs and anti-oxidant vitamins. Between September 1993 and August 1995, 1006 families consisting of the two biological parents with at least two children were recruited totalling 4295 individuals. This cohort will be followed up until 2004. There will be two health examinations five and ten years after the initial examination. A bank of blood samples (serum and plasma) in liquid nitrogen and DNA (−80 °C) has been established.

BACKGROUND There seems to be a consensus that family influences on dietary habits are important but few studies have addressed this issue directly. The purpose of this study was to determine if and how dietary intake aggregates within families. METHODS We examined the family aggregation of energy intake and the proportion of protein, fat and carbohydrate in the diet, estimated by a 3-day food consumption diary in 387 middle-class French families. RESULTS For energy and all macronutrients, spouse-spouse and child-child correlations were higher than parent-child correlations suggesting the minor contribution of genetics and the preponderant role of cultural and residual random environment. Variance component analysis confirmed the absence of genetic component for energy and all macronutrients and underlined the important role of a cohabitational effect for parents. Cultural inheritance represented 30-40% of dietary intake variance for children. Families who shared meals together more often had a lower residual random component. With the increasing number of meals eaten together (> 45/week versus < or = 45/week), between-generation components increased by about 10% for fat and carbohydrate, while for protein intake, the between-generation component for both parents (about 27%) and children (about 37%) remained unchanged. CONCLUSIONS The general finding that dietary intake aggregates within families and that the individual behaviours are greatly influenced by characteristics within the family unit such as the number of meals eaten together provides additional justification for health promotion programmes that target the family as the unit for intervention.

The effects of alcohol consumption on serum concentrations of apolipoproteins (apo) A-I, C-III, B, and E and of lipoproteins (Lp) A-I, A-I:A-II, C-III, C-III:B, and (a) were studied in 132 healthy subjects, including 55 low drinkers of alcohol (50 g/day), and in 97 hospitalized alcoholic patients (> 100 g/day) without severe liver disease (especially functional insufficiency), before and after 21 days of withdrawal treatment. Serum concentrations of apo A-I, LpA-I, LpA-I:A-II, apo C-III, and LpC-III significantly (P

Many recent in vitro experiments support the hypothesis that oxidatively modified low density lipoproteins (LDLs) could participate in atherogenesis. Oxidation of LDLs, especially derivatization by aldehydes originating from peroxidation of fatty acids and fragmentation of apolipoprotein (apo) B-100 which is their major apolipoprotein, probably occurs extravascularly and the presence of oxidized LDLs in the circulation is not well documented. Using electrophoresis and immunodetection techniques, we studied the structure of apo B and the presence of adducts of malondialdehyde (MDA) to this protein in LDLs from plasma of a limited population of five healthy subjects and nine patients with severe atherosclerosis. In the patient-derived LDLs, apo B appeared extensively fragmented, much more so than in those from the healthy subjects, although LDLs were isolated in all cases in the presence of antioxidants, protease inhibitors and antibiotics. Additionally, in all healthy subjects, we found a minor fragment of apo B-100, apo B-74, whereas the complementary peptide, apo B-26, was not detected; thus the presence of this minor form cannot be related to cleavage of apo B-100, either by proteolysis or by oxidation. We also present evidence that MDA adducts are present in circulating apo B and most of its fragments not only in atheromatous patients, but also in healthy subjects. Our results are consistent with the existence of oxidized LDLs in the human circulation. However, the role of non-oxidative phenomena in the structural modifications affecting apo B which are reported here cannot be excluded.

Superoxide dismutase, glutathione peroxidase and catalase are the three main enzymatic systems of defense of the organism against free radicals and peroxides. A survey of the literature shows that no general tendency of evolution of these systems in aging emerges, even if some recent studies in humans demonstrate the existence of a concomitant decrease in most of the antioxidant enzymes in blood of the elderly. The study of the antioxidant systems and their interrelations in the elderly represents a large field of future investigations.

Abstract The objective of this study was to determine whether systolic pressure and left ventricular mass in children, adolescents, and young adults are related to fetal and infant growth. Blood pressure measurements and M-mode echocardiography were performed in 210 subjects aged 8 to 24 years whose information on weights at birth and in early infancy, written by physicians, was obtained from the children’s health record booklets. Systolic pressure, adjusted for sex and current height or for sex, current age, weight, and height, was the highest in subjects with low birth weight. No association was observed between systolic pressure and weight at either 9 months or 2 years. Left ventricular mass, adjusted for sex and current height or for sex, current age, weight, and height, increased with decreasing weight at 9 months or 2 years, independent of systolic pressure. Increased ventricular mass associated with reduced infant growth was concentric, resulting from a proportionate thickening of the posterior wall and interventricular septum. Left ventricular mass was not related to birth weight. These findings were observed in both sexes and in all age subgroups and were independent of gestational age, birth order, and parental risk factors. This study supports the hypothesis that systolic pressure and left ventricular mass might be partly determined during fetal life and early infancy. The mechanisms that underlie the associations of blood pressure and left ventricular structure with weights at birth and in early infancy should be studied thoroughly.

Background: Among adolescents, social differences in physical activity (PA) and sedentary behaviour (SB) are seldom explained. Proportionate universal interventions aimed at reducing social inequalities among overweight adolescents are uncommon. Objectives: To explore correlations between PA, SB, social, family and school-related factors among adolescents. Four research topics were elaborated: identifying factors associated with PA and SB, analysing socially less-advantaged overweight adolescents’ participation in a proportionate universal school intervention, analysing adolescents' perceptions of their PA practice, and evaluating the effectiveness of this intervention. Methods: This work is the result of two trials in the school setting: (PRomotion de l'ALIMentation et de l'Activité Physique) and PRALIMAP-INÈS (INÈgalité de Santé). The International PA Questionnaire (IPAQ) was used to measure PA and SB. Social status was defined according to socio-professional categories and the family affluence scale (FAS). Data on perceptions was collected from individual interviews. Individual interviews allowed data collection of perceptions. Logistic regressions were also carried out. Results: PA was dependent on social, family and school-related characteristics. Total energy expenditure was not sufficient to identify social differences in PA. The perceived barriers to PA practice were mostly individual and were different according to social status and gender. The proportionate universal intervention in schools successfully engaged these adolescents and reduced social inequalities related to PA. Conclusion: This work emphasises the importance of implementing specific activities in PA for socially less advantaged overweight adolescents, Contexte : Chez les adolescents, les différences sociales dans les pratiques d’activité physique (AP) et les comportements sédentaires restent peu expliquées. Les interventions universelles proportionnées visant la réduction des inégalités sociales chez les adolescents en situation de surpoids/obésité sont rares. Objectifs : Explorer les relations entre l’AP, la sédentarité, les facteurs sociaux, familiaux et scolaires chez les adolescents. Quatre axes de recherche ont été définis : identification des facteurs associés à l'AP et à la sédentarité, étude de la participation des adolescents en situation de surpoids/obésité socialement moins favorisés à une intervention universelle proportionnée en milieu scolaire, analyse de la perception des adolescents de leurs pratiques et évaluation de l'efficacité de l'intervention. Méthodes : Ces travaux sont issus d’essais en milieu scolaire : PRALIMAP (PRomotion de l'ALIMentation et de l'Activité Physique) et PRALIMAP-INÈS (INÈgalité de Santé). Le questionnaire international d’AP (IPAQ) a été utilisé pour mesurer l’AP et la sédentarité. Le niveau social a été défini à partir des catégories socioprofessionnelles et de l’échelle d’aisance familiale (FAS). Des entretiens individuels ont permis le recueil des perceptions. Des régressions logistiques ont été réalisées. Résultats : L'AP était dépendante des caractéristiques sociales, familiales et scolaires. La dépense énergétique totale n’était pas suffisante pour identifier les différences sociales en AP. Les freins perçus à la pratique d’AP étaient majoritairement individuels et étaient différents selon le niveau social et le sexe. Une intervention universelle proportionnée en milieu scolaire a permis la mobilisation de ces adolescents et de réduire les inégalités sociales d’AP. Conclusion : Ces travaux soulignent l’importance de la mise en œuvre en milieu scolaire d’actions spécifiques en AP pour les adolescents en situation de surpoids/obésité socialement moins favorisés