Authors: Veronique Thomas-Ollivier PhD ; Marina Fortes PhD
Institution: University of Nantes
Country: France
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Fuente: Foro Mundial de Educación Física; II Cumbre Iberoamericana de Educación Física y Deporte Escolar; Simposio de Actividad Física y Calidad de Vida; Taller Internacional de  Deporte Escolar y Alto Rendimiento, 2010.

For several years the prevalence of the obesity increases regularly in France. The part of persons in overweight in the adult population is crossed from 8,5 % in 1997 to 14,5 % in 2009 (results of the survey of ObEpi-Roche on 2009). It is urgent to achieve to a better understanding of the multiple factors at the origin of the weight gain to set up actions of adapted and effective prevention. The physical activity is unmistakably an important factor of fight against obesity. The report of evaluation of the national program nutrition health (2006-2010) coordinated by the Ministry of Health and the sports shows that the physical activity adapted for the persons in overweight is still too little developed. Physical activity appears to be an important contributor in the treatment for obesity. Although weightloss directly attributable to increased physical activity may be small, physical activity further enhances psychological well-being, improves self-esteem and reduces feelings of anxiety and depression.
Most researches are based on nomothetic approaches interested in the average change of psychological determinants or generic functioning of the self-concept.
Considering that self-esteem presents long-term fluctuations (Rosenberg, 1986) and appears to be sensitive to daily (bad or good) events (Nezlek & Plesko, 2001), one objection to these classical approaches of psychological constructs (i.e. self, anxiety, depression) is that they only focused on changes of magnitude and not on the processes underlying emergence over time. According to Slifkin and Newell (1998), variability in living systems cannot be understood without considering the timeevolutionary properties of behaviour.


This study has two aims:

1-to characterize the effects of the physical activity on the well being of obese persons through the measure of the self, the quality of life, the level of anxiety and depression before and after the practice of a physical activity;
2-to propose a first exploratory approach which analyzes the evolution of selfesteem, depression, anxiety and physical self, over time in the aim to understand the role of physical activity on obese adults psychological functioning.

Six obese adults (5 woman, 1 man; mean age of 46.8 9.3) were recruited from a larger pool of 30 obese adults who participated in a 6-month physical activity program in 2008-2009. Participants were volunteered for this study. They gave informed written consent to participate. Participants were included if they were: (a) obese (BMI>30 kg/m2), (b) between the ages of 18 and 75 years and (c) not submitted to any insulinotherapy treatment or sulfamides or any other invalidating pathology.

All participants filled the two following questionnaires at the beginning and the end of the program: (i) the Self State Questionnary (QES-20, Fortes, Hauw and Ninot, 2009) which measures global self-esteem, social, physical, familial and professional self, (ii) the Hospital Anxiety and Depression (HAD) Scale (Lepine, Godchau, & Brun, 1985; Zigmond & Snaith, 1983).

From the beginning of the program, each participant completed a booklet in which each page contained six 10-cm visual analog scale measuring depression, anxiety, self-esteem and social, familial, and physical self. The subjects were asked to answer twice a day, between 7:00 and 9:00 (AM and PM), over a three-month period.
The six items were presented successively in random order, and participants had to respond on a visual analog scale anchored by "not at all" at the left extremity and "absolutely" at the right. We obtained 168-point time series for each scale and each participant.
Time series analyses. The ARIMA procedures (Box & Jenkins, 1976) were realized for each individual scale and allowed to model construct evolution. These analyses are based on the study of the autocorrelation (ACF) and partial autocorrelation functions (PACF), which inform about the temporal dependence of the series. An ARIMA model is composed of the potential association of three kinds of mathematical processes: auto-regressive (AR), integrated (I) and moving average (MA) processes. The model is labeled as (p, d, q) where p indicates the number of auto-regressive terms, d the number of differentiations, and q the number of moving average terms. The models resulting from analysis are constituted from the combination of these three processes. For example, an ARIMA model (0,1,1) obeys the following equation:
yt = + y(t-1) - (t-1) + where is the mean of the series, 1 the moving average coefficient and t the error at time t.

Results and discussion
Results from the evaluation before / after physical activity workshops revealed a significant effect of the physical self dimensions (t = 3.1; p = 0.003) and the family self (t = 2.8; p = 0.03). The level of anxiety increases after the physical workshops (t = 2.70; p = 0.003). No effect is observed on the depression, the quality of life, global self esteem and social and professional dimensions of the self-esteem A representative time series is presented in Figure 1. As can be seen, the series appeared generally non-stationary, with constantly marked evolutions.

Figure 1: A representative time series (subject 2, global self-esteem)

The results showed that autoregressive models without differentiation and with a significant constant provided a satisfactory support accounting for the dynamics of 93.3% of the series (p < .01). Surprisingly, results revealed seasonality components necessary to give an account of 46.7% of the series (p < .01).
As such, the resulting models could be presented as follows:

y t = 1y(t-1) + t .17 < < .54 (16 series) (2)
yt = μ + y(t-1)+ y (t-14) + t .19 < < .42 (14 series) (3)
Autoregressive models suggest that past value (past self-evaluation) entirely determines current value. It reveals short-time dependencies and the absence of stable reference like personality trait.

The results obtained on questionnaires before / after practice do not emphasize a massive effect of the physical activity on psychological well being, anxiety or depression. Some explanatory hypotheses can be advanced. The patients practised a physical activity of low intensity and frequency. This amount of practice was not enough important to enhance psychological well-being highlighted by OMS recommendations.
The improvement of physical and familial dimension of the self let think that a more regular practice would allow a more important diffusion of this effect on the other dimensions of the self.
The exploratory study on the evolution of the global self esteem for 6 months reports the importance of the daily events and their effect on the dynamics of the self. The strong variability (figure 1) and the short-term historicity show that the obese persons do not present a "stable" functioning but daily "build themselves" or "adapt themselves” to their pathology.
These results are opposed to Fortes and her collaborators conclusions (Fortes, Delignières and Ninot, 2004). These authors have shown that healthy self-concept dynamics was fitted by a differenced first-order moving average model. It suggested a kind of individual disposition related to the stability of self-esteem and its resistance to the influence of daily events. They conclude that dynamics of the series seem organized around a locally stable reference value, a kind of transient trait that evolves progressively under the influence of life events.
Surprisingly, the results of our study emphasize the importance of daily events independently to exercise sessions and highlight constant changes of depression, anxiety and self. Obese adults psychological functioning can be characterized by strong and permanent fluctuations. This great variability and short-term historicity (time dependence) show that obese adults have not stable self-evaluations or representations but rather “build” themselves everyday or continuously. They “adapt”themselves to daily perturbations or displaying chronic psychological patterns which were revealed by seasonality.
Besides, physical self that was supposed to be more affected or influenced by physical activity program shares similar dynamics than other dimensions for a same subject. In this way, this study reveals the general extreme vulnerability of obese adults when considering psychological dimensions.
It underlines the limits to realize nomothetic or group studies and can explain the lack of consensus when considering results of researches having measured the effect of different program (diet, exercise…) on psychological changes from few evaluations.
This exploratory research first emphasizes the relevance of an idiographic protocol design to provide a potent means to more fully understand the functioning of psychological constructs such as the self. Second, as advocated by Slifkin & Newell (1998), the need to consider the assessment of both the amount and the dynamic structure of self-evaluative variability.


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