Léna Pélissier

Un nombre significatif et croissant de personnes "normo-pondérées", présentant un indice de masse corporelle entre 18.5 et 24.9 kg.m-², est engagé dans des pratiques de régime pour perdre du poids. Alors que certains travaux de recherche ont suggéré un risque considérable de (re)prise de poids, et notamment de masse grasse, lié à ces pratiques, il y a un réel besoin de mieux déterminer et comprendre les effets d'une perte de poids dans cette population. Les travaux de thèse ont permis d'apporter de nouvelles connaissances sur l'évolution du poids et de la composition corporelle, les adaptations énergétiques et la régulation de la prise alimentaire en réponse à une restriction calorique et un mois de suivi post-interventionnel chez des hommes et femmes normo-pondérés. La perte de poids de 3% et 6% du poids initial a induit une perte de tissus maigres et adipeux, associée à des adaptations sur les deux versants de la balance énergétique (dépense et apports d'énergie). À court terme après l'intervention, la diminution de la restriction cognitive liée à l'alimentation était associée à une reprise de poids, questionnant la durabilité de la mise en place d'un régime. Bien que ce rebond de poids ne fût constitué que de masse maigre, les présents résultats n'écartent pas un risque de reprise de masse grasse à plus long terme. Ainsi, ce travail de doctorat a permis de formuler des premières recommandations pour la population normo-pondérée désirant perdre du poids par un régime et a apporté de nouvelles perspectives dans la caractérisation et la compréhension des effets liés à ces pratiques.

Depending on the nature of their sports, athletes may be engaged in successive weight loss (WL) and regain, conducing to “weight cycling.” The aims of this paper were to systematically (and meta‐analytically when possible) analyze the post‐WL recovery of (i) body weight and (ii) fat mass; fat‐free mass; and performance and metabolic responses in weight cycling athletes (18–55 years old, body mass index < 30 kg.m⁻²). MEDLINE, Embase, and SPORTDiscus databases were explored. The quality and risk of bias of the 74 included studies were assessed using the quality assessment tool for quantitative studies. Thirty‐two studies were eligible for meta‐analyses. Whatever the type of sports or methods used to lose weight, post‐WL body weight does not seem affected compared with pre‐WL. While similar results are observed for fat‐free mass, strength sports athletes (also having longer WL and regain periods) do not seem to fully recover their initial fat mass (ES: −0.39, 95% CI: [−0.77; −0.00], p = 0.048, I² = 0.0%). Although the methods used by athletes to achieve WL might prevent them from a potential post‐WL fat overshooting, further studies are needed to better understand WL episodes consequences on athletes' performance as well as short‐ and long‐term physical, metabolic, and mental health.

While there is an increasing prevalence of dieting in the overall population, weight loss (WL) practices could be a risk factor for weight gain (WG) in normal-weight (NW) individuals. The aim of the present work was to systematically review all the studies implicating diet restriction and body weight (BW) evolution in NW people. The literature search was registered in PROSPERO (CRD42021281442) and was performed in three databases from April 2021 to June 2022 for articles involving healthy NW adults. From a total of 1487 records initially identified, eighteen were selected in the systematic review. Of the eight dieting interventional studies, only one found a higher BW after weight recovery, but 75 % of them highlighted metabolic adaptations in response to WL favouring weight regain and persisting during/after BW recovery. Eight of the ten observational studies showed a relationship between dieting and major later WG, while the meta-analysis of observational studies results indicated that ‘dieters’ have a higher BW than ‘non-dieters’. However, considering the high methodological heterogeneity and the publication bias of the studies, this result should be taken with caution. Moreover, the term ‘diet’ was poorly described, and we observed a large heterogeneity of the methods used to assess dieting status. Present results suggest that dieting could be a major risk factor for WG in the long term in NW individuals. There is, however, a real need for prospective randomised controlled studies, specifically assessing the relationship between WL induced by diet and subsequent weight in this population.

School-based multi-component educational interventions have been encouraged to improve children’s movement behaviors. The present study evaluates the effect of the Globe Trotter Initiative on physical activity (PA) level, sedentary time, physical fitness and activity preferences in primary school children. A total of 361 children (9–10 years) participated in this cluster-randomized trial. Nine schools were randomized as control (CON, 121 children) or Globe Trotter schools (GT, 240 children). Physical fitness, body composition, anthropometric characteristics, PA level, sedentary behaviors, physical self-perception, and activity preferences were evaluated at baseline (T0) and after the one-month intervention (T1). Grip strength performance and overall completion time of the obstacle course show a significant time effect (p < 0.001) in both groups (no group effect). PA level and physical self-perception did not significantly show time nor group effects. The sedentary behavior score displays a significant “time × group” interaction effect (p = 0.04) with a significant reduction between T0 and T1 in the GT group only (p < 0.001). The explicit liking for sedentary activities shows a significant “time × group” interaction (p = 0.02) with a significant decrease between T0 and T1 in the GT group only (p < 0.001). The explicit wanting for sedentary activities show a significant “time × group” interaction (p = 0.02) with a significant decrease between T0 and T1 in the GT group only (p < 0.001). The short-term, multi-component, behavioral, educational GT intervention had beneficial effects on primary-school-aged children’s sedentary time and implicit preference for physical over sedentary activities.

The first emergency was to receive and treat COVID-19 patients in their acute phase; today, there is a clear need to propose appropriate post-acute rehabilitation programs. The aim of this research was to systematically review the effects of physical activity programs in the recovery of post-COVID-19 patients. The literature search followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines, was registered in the PROSPERO database (CRD42022289219), and was conducted between August and December 2021. A total of 35 studies out of the 1528 initially identified were finally included in the analysis. The systematic review clearly showed the health benefits of rehabilitation including physical activity in post-COVID-19 recovery, regardless of exercise modalities. These positive results were even observed using minor muscle re-mobilization for severe cases (i.e., postural changes, few steps—2 times/day) or using low volumes of exercise for mild-to-moderate cases (i.e., 120 min/week). A total of 97% of the 29 studies that performed statistical analyses demonstrated a significant increase in at least one parameter of functional capacity, and 96% of the 26 studies that statistically investigated the effects on the quality of life, mental health, and general state reported improvements. Yet, most of the studies were retrospective, uncontrolled, and enrolled aged people with comorbidities presented in severe forms of COVID-19. Physical activity programs, in addition to their high heterogeneity, remained poorly described in 83% of the studies and were part of a multidisciplinary program for 89% of the studies. Despite promising results, there is today a real need for prospective well-designed studies specifically assessing the effects of physical activity. In addition, it might appear relevant to propose standardized programs further considering the main characteristics of patients such as age, comorbidities, or the severity of COVID-19.

Rapid weight loss (RWL) is a common precompetitive strategy used by athletes in weight-class sports and carries with it an increased risk to future cardiometabolic health. The Rapid Weight Loss Questionnaire (RWLQ) is a self-reported tool designed to identify and characterize such weight loss practices. After developing a reliable and reproducible French version of the RWLQ (RWLQ-FR), the present study aims to analyse RWL patterns among French weight-class athletes and to point out potential relationships between such practices and risk of subsequent weight gain. A test-retest analysis was performed in 54 athletes to test the questionnaire reproducibility before applying it in a cohort of 168 weight-cycling athletes (23.78±9.25 y, 67.6±12.6 kg, 81 males and 87 females, n=24 strength sports and n=144 various combat sports). Results showed good agreement of the RWLQ-FR (Rho=0.794, [0.696-0.893]). Athletes reported losing an average of 4.1±2.9% of their initial weight in 13.1±9.6 days, with the main methods used being an increase in exercise, training in rubber or plastic suits, and gradual dieting. The average weight recovery in a week was 3.5±2.8% and results showed that the athletes with the lower inter-season weight (weight outside of the training and competition season) regained the more weight (p=0.025). The average RWLQ-FR score was 31.9±17.3 and athletes who began to lose weight earlier in their competitive carrier had the higher scores (p=0.032). To conclude, the present study demonstrates relationships between the pattern of RWL practices and potential increased risk of subsequent weight gain in weight-cycling athletes, and the need to better understand the long-term health-related risks.

The aim of the present study was to evaluate whether the COVID-19-related confinement and social restrictions affected the levels of physical fitness and academic achievement in primary school French children. A total of 206 primary school children (106 before confinements and 100 after restrictions) completed a test battery evaluating their anthropometric characteristics, body compositions, activity preferences, cognitive performances and physical fitness. The performance of the Standing Long Jump was better at T0 (169.9 ± 142.5 cm) compared to T1 (135.2 ± 31.4 cm) (p = 0.0367), and the Medicine Ball Throw performance declined from T0 to T1 (297.3 ± 81.1 cm vs. 249 ± 52 cm; p < 0.0001). Motor skills (26.9 ± 6.2 s vs. 30.9 ± 5.4 s; p < 0.0001), the shuttle-run test (stages completed), Maximal Aerobic Speed, and the estimated VO_2max were lower at T1 compared to T0 (p < 0.0001). Executive functioning was found to be greater at T0 compared to T1 (p < 0.0001). Explicit liking or wanting for sedentary or physical activities did not change between T0 and T1. Both overall physical fitness and cognitive performance drastically declined among primary school French children with the COVID-19-related public health restrictions, which reinforces the need to urgently develop preventive strategies in anticipation of further mitigation measures.