The last decades have been characterized by a global growing obesity epidemic, starting already in childhood
]. World-wide at least 110 million children are overweight or obese
]. In the European Union, the prevalence of childhood overweight and obesity ranges from 10-20% (northern European areas) to 20-40% (Mediterranean Sea countries) and is expected to rise by 1.3 million children per year
]. These numbers stress the importance of a better understanding of the complex etiology of obesity in order to help developing effective prevention programs. In addition, evidence confirmed the importance of focusing obesity prevention on young age groups, as obese children were found to be at increased risk of becoming obese adults (“tracking phenomenon”)
] and to experience increased metabolic complications in adulthood
]. To simplify, overweight and obesity will be covered by the term ‘obesity’ in this article.
Excessive caloric intake, insufficient physical activity and sleep deprivation are major lifestyle factors involved in the development of obesity
]. Recently, the effects of chronic psychosocial stress have been increasingly recognized, also in children
]. Chronic exposure to stress may disrupt the physiological stress system, influencing food intake regulation (increased energy intake and craving for ‘comfort foods’)
] and fat deposition in the body (favoring central obesity)
]. However, there is a need for more scientific research into the mechanisms linking chronic stress to appetite regulation, energy balance and consequently body composition in humans and more importantly in children.
The stress-obesity relationship is characterized by direct and indirect pathways (Figure
). The direct
effect of stress on body fatness and consequently the development of obesity is largely caused by the end-product of the hormonal stress response, i.e. cortisol
]. Cortisol favors visceral fat disposition and stimulates appetite
]. In addition, stress may indirectly
facilitate the development of obesity by influencing other lifestyle factors such as diet, physical activity and sleep
]. After all, stressed persons may consume more so-called “comfort foods”, as these foods stimulate rewarding and pleasure sensations
]. Furthermore, stressed persons may be less motivated or have less energy to do physical activity and may suffer from sleeping problems
]. Inversely, these lifestyle factors may also influence the stress load. Physical activity may be a protecting factor against obesity and stress by increasing energy expenditure and by improving mental health and stress coping
]. On the contrary, lack of sleep may reduce coping capacity and thus resistance against stress
Lifestyle factors involved in the development of obesity and investigated in the ChiBS project Grey arrows indicate the study hypotheses, black arrows show the effect of the four lifestyle factors on obesity.
The ChiBS study (Children’s Body composition and Stress) is designed to investigate the relationship between chronic psychosocial stress in young children (6-12
years old) and changes in body composition (body fat) over a two-year follow-up period (2010-2012). It is hypothesized that the exposure to chronic stressors may affect children’s body composition in the long-term by promoting body fatness increase and the development of obesity. More specifically, this study will examine the influence of chronic stress on the evolution of different body composition parameters longitudinally, taking into account diet, sleep and physical activity as intermediary factors in this relationship. It is hypothesized that chronic stress may promote consumption of energy dense highly palatable (sugar and fat rich) foods and a deviant eating behavior, decreased quantity and quality of sleep and a decreased amount of physical activity, as indicated in Figure
. To accurately measure stress, child- and parent-reported stress questionnaires as well as objective stress biomarkers from different biological matrices are used. A second, parallel aim is to test the feasibility and interrelationships of these different stress measurements in children. Finally, the third aim is to further unravel the impact and mutual relationships of physical activity, diet, sleep and stress.
This paper describes the design of the ChiBS study, its instruments, measurements, population characteristics, and participation and drop-out rates for each examination module.