Doctor: Cécilia Saldanha-Gomes

Title: Physical Activity, Television Exposure and Diet in Preschool Children : Impact on Adiposity

Supervisors: Patricia Dargent, Sandrine Lloret

Doctoral school: ED 420. Doctoral school of Public health, University Paris Saclay

Date of thesis defense: 19/12/2019

Jury: Patricia Dargent-Molina, Jean-Michel Oppert, Marie-Josèphe Saurel-Cubizolles, Sandrine Peneau, Isabelle Aubin-Auger, Denis Devictor, Sandrine Lioret, Vincent Gajdos

Thesis summary:

The epidemy of obesity concerns also young children, is characterized by important social inequalities and has important consequences on health in the short, medium and long-term. Energy balance-related behaviors, namely physical activity, television exposure and diet, may be important in young children in determining subsequent obesity risk, and are potentially modifiable. The objective of this work was to examine the association between energy balance-related behaviors, considered in isolation or in combination (via cluster analysis) at 2 and 5 years of age, and obesity risk in boys and girls separately. Obesity risk was assessed by the percentage of body fat at 5 years and the age of the adiposity rebound. The work is based on data from the EDEN birth cohort. At 2 years, outdoor play time and television watching time were respectively, inversely and positively associated with the percentage of body fat at 5 years. At 2 years, 2 clusters emerged that were essentially characterized by opposite eating habits, with intake of energy-dense food and sweetened beverages being the most discriminating feature. At 5 years, clusters (2 in boys, 4 in girls) were mainly differentiated by the level of television exposure; in boys, high television exposure combined with unhealthy eating habits, while in girls, all possible combinations of the level of television exposure and time spent in outdoor physical activity (play and walk) were observed within clusters. Girls belonging to the ‘Very high television exposure – High outdoor physical activity’ cluster had a significantly higher percentage of body fat than girls in the reference cluster (labeled ‘Moderate television exposure – rather high outdoor physical activity’). Furthermore, a higher score on the ‘Processed and fast foods’ pattern (identified in a previous Eden analysis) at 2 years was associated with an earlier age of adiposity rebound (here defined as before 3.7 years on the average in both sexes). Maternal education level (taken as a general indicator of socio-economic position (SEP)) was inversely related to television viewing time as well as clusters characterized by a high level of television and/or less favorable eating habits (eating while the television is on and drinking sweetened beverages at mealtimes). These results suggest that all three-energy balance-related behaviors influence the subsequent risk of obesity, but with different timing of influence, on distinct markers of obesity risk, and in a way that differ according to the child’s sex and his/her family’s SEP. Furthermore, results suggest that these behaviors combine in complex ways that differ in boys and girls, and that identification of behavioral typologies based on specific combinations of behaviors may be useful to distinguish groups of children with different levels of risk. These results plead for integrated obesity preventive strategies targeting all three-energy balance-related behaviors, and implemented as early as possible, ideally before the age of 2. Efforts should strive to decrease television viewing time, especially in low SEP families, while simultaneously promoting physical activity, in particular by encouraging young girls to engage in active outdoor play. In parallel, it appears important to encourage mothers, especially from low SEP families, to follow diet guidelines and adopt favorable mealtime routines (e.g., turning off the television during meals, and proposing water rather than sodas at mealtime). Because of their frequent and continued contact with parents and their children throughout childhood, family physicians are particularly well positioned to help parents promote and support the development of early healthful physical activity and diet habits of children, starting in early childhood.

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