Food habits and sport activity during adolescence: differences between athletic and non-athletic teenagers in Switzerland.

OBJECTIVE: To describe food habits and dietary intakes of athletic and non-athletic adolescents in Switzerland. SETTING: College, high schools and professional centers in the Swiss canton of Vaud. METHOD: A total of 3,540 subjects aged 9-19 y answered a self-reported anonymous questionnaire to assess lifestyles, physical plus sports activity and food habits. Within this sample, a subgroup of 246 subjects aged 11-15 also participated in an in-depth ancillary study including a 3 day dietary record completed by an interview with a dietician. RESULTS: More boys than girls reported engaging in regular sports activities (P<0.001). Adolescent food habits are quite traditional: up to 15 y, most of the respondents have a breakfast and eat at least two hot meals a day, the percentages decreasing thereafter. Snacking is widespread among adolescents (60-80% in the morning, 80-90% in the afternoon). Food habits among athletic adolescents are healthier and also are perceived as such in a higher proportion. Among athletic adolescents, consumption frequency is higher for dairy products and ready to eat (RTE) cereals, for fruit, fruit juices and salad (P<0.05 at least). Thus the athletic adolescent's food brings more micronutrients than the diet of their non-athletic counterparts. Within the subgroup (ancillary study), mean energy intake corresponds to requirements for age/gender group. CONCLUSIONS: Athletic adolescents display healthier food habits than non-athletic adolescents: this result supports the idea that healthy behavior tends to cluster and suggests that prevention programs among this age group should target simultaneously both sports activity and food habits.

Three essays on the psychology of investment and financial markets

Préface My thesis consists of three essays where I consider equilibrium asset prices and investment strategies when the market is likely to experience crashes and possibly sharp windfalls. Although each part is written as an independent and self contained article, the papers share a common behavioral approach in representing investors preferences regarding to extremal returns. Investors utility is defined over their relative performance rather than over their final wealth position, a method first proposed by Markowitz (1952b) and by Kahneman and Tversky (1979), that I extend to incorporate preferences over extremal outcomes. With the failure of the traditional expected utility models in reproducing the observed stylized features of financial markets, the Prospect theory of Kahneman and Tversky (1979) offered the first significant alternative to the expected utility paradigm by considering that people focus on gains and losses rather than on final positions. Under this setting, Barberis, Huang, and Santos (2000) and McQueen and Vorkink (2004) were able to build a representative agent optimization model which solution reproduced some of the observed risk premium and excess volatility. The research in behavioral finance is relatively new and its potential still to explore. The three essays composing my thesis propose to use and extend this setting to study investors behavior and investment strategies in a market where crashes and sharp windfalls are likely to occur. In the first paper, the preferences of a representative agent, relative to time varying positive and negative extremal thresholds are modelled and estimated. A new utility function that conciliates between expected utility maximization and tail-related performance measures is proposed. The model estimation shows that the representative agent preferences reveals a significant level of crash aversion and lottery-pursuit. Assuming a single risky asset economy the proposed specification is able to reproduce some of the distributional features exhibited by financial return series. The second part proposes and illustrates a preference-based asset allocation model taking into account investors crash aversion. Using the skewed t distribution, optimal allocations are characterized as a resulting tradeoff between the distribution four moments. The specification highlights the preference for odd moments and the aversion for even moments. Qualitatively, optimal portfolios are analyzed in terms of firm characteristics and in a setting that reflects real-time asset allocation, a systematic over-performance is obtained compared to the aggregate stock market. Finally, in my third article, dynamic option-based investment strategies are derived and illustrated for investors presenting downside loss aversion. The problem is solved in closed form when the stock market exhibits stochastic volatility and jumps. The specification of downside loss averse utility functions allows corresponding terminal wealth profiles to be expressed as options on the stochastic discount factor contingent on the loss aversion level. Therefore dynamic strategies reduce to the replicating portfolio using exchange traded and well selected options, and the risky stock.

Le sport, un enjeu de santé publique ?

Les bénéfices pour la santé d'une activité physique régulière sont de mieux en mieux établis et s'appliquent notamment à des pathologies aussi diverses que l'infarctus du myocarde ou certains cancers. Or, deux tiers de la population suisse rapportent une pratique en activité physique inférieure aux recommandations minimales pour la santé. On estime en Suisse que la sédentarité est annuellement responsable de 2,1 millions de cas de maladie, de 2900 décès et de 2,4 milliards de francs de coûts liés aux traitements.

Lésions de surcharge chez l'enfant [Overuse injuries in children].

The physical-activity and sporting at the child and the teenager is probably, in these years 2000, in full change. In a paradoxical way, extremely sporting children or teenagers are living beside extremely sedentary school-boys, neglecting the majority of the physical-activities and preferring a home-lifestyle. In the evaluation of overload sporting lesion of at teenager, it is thus imperative to take into account not only the individual characteristics of the child: its sex, its age, its stage of growth, its psychology, the presence or not of preexistent pathologies or anatomical disorders. It is naturally necessary to wonder about the training methods of the activity, but it appears fundamental to me to evaluate the child from a sensitivo-motor point of view and this can be carried out by assessments physio-therapeutic or aptitude tests carried out by doctors of the sport.

The determinants of sport participation in Switzerland

This paper aims at investigating the socio-cultural factors that affect leisure-time sport participation in Switzerland. Data drawn from 8 waves of the Swiss Household Panel is used to evaluate a probit model with random effects, that takes into account the socioeconomic and demographic characteristics of the respondents. In line with existing literature, findings from the multivariate analysis show inequalities in sport involvement in Switzerland. These are significantly related to age, income, education, citizenship and cultural aspects. Appropriate and targeted policies promoting participation in sports among the community can be found on the basis of the critical modifiers in the model and their impact.

Social sensing for psychology: Automated interpersonal behavior assessment

In this article, we show how the use of state-of-the-art methods in computer science based on machine perception and learning allows the unobtrusive capture and automated analysis of interpersonal behavior in real time (social sensing). Given the high ecological validity of the behavioral sensing, the ease of behavioral-cue extraction for large groups over long observation periods in the field, the possibility of investigating completely new research questions, and the ability to provide people with immediate feedback on behavior, social sensing will fundamentally impact psychology.