Physical Activity, Fitness, Nutrition and Obesity During Growth

Secular trend of body height was analyzed using the results of six Nationalwide Anthropological Surveys in the Czech Republic (NAS) conducted in ten-years intervals from 1951 to 2001. These data documented, similarly as in other countries a continuing increase of body height, as a result of improving socio-economic conditions. Highest increase of body height has occurred especially during puberty, due to the shift of the start and of the individual stages of puberty to an earlier age. A shift to an earlier age was revealed also in the age of adiposity rebound (AR), by more than one year earlier in both genders. Along with these changes, adiposity evaluated by skinfolds has been increasing, starting with preschool children; body mass index (BMI) during the same period fluctuated insignificantly and has not revealed clearly changes of body composition. Along with that, an alarmingly increasing prevalence of obesity in children and adolescents has appeared as a result of imbalance between energy intake (EI - nutrition) and energy expenditure (EE) due to sedentarism starting early in life.

With increasing prevalence of overweight and obesity the evaluation of the relationship of body weight to body height using body mass index (BMI) has spread universally also in children.In youngest children, maximally up to the age of 5 years only a relationship weight-for-length/height is used. In children the values of BMI are markedly dependent to the age and are specific for gender. Therefore utilization of growth reference is critical for assessment of health and nutritional status of children. In addition to the national growth references for children up to 19 years growth references WHO 2007, CDC 2000 and IOTF 2000 are mostly used. The WHO growth standards for children 0 – 5 years old were published in 2006. International comparisons of the evaluation of overweight and obesity are difficult due to the lack of consent of criteria used. In children after birth and during first year the percentile curves of BMI increase very markedly, but then they decrease. The second rise in BMI curve, i.e. adiposity rebound (AR), occurs between 5 and 7 years. An early AR is associated with an increasing risk of overweight. The secular trend of increased height and accelerated growth are probably responsible for shift of AR at earlier age. Until present overweight and obesity were the problem especially in high-income countries, overweight and obesity are now on the rise in low- and middle-income countries, particularly in urban settings. Selected studies from developed countries indicate, that this trend is finished.

Assessment of energy intake and energy expenditure is crucial for recommendation of weight maintenance and weight loss regimen. Energy intake but also proportion and composition of individual nutrients is essential for effective weight management and diet recommendation, which should be applied during earliest periods of life. In this respect, nutritional status of the mother, factors during fetal and perinatal period play an important role from the point of view of actual, but also future consequences. Individual nutrients as well as their composition with regard to their present and delayed effect are summarized in the chapter. Diet – energy intake and nutrient composition should be considered and related to energy expenditure.

The objective of the chapter is to describe the basic objective means for long-term, as well as short-term field-based monitoring of physical activity in children and adolescents and to formulate education and health-related recommendations to promote an active lifestyle. The first part of the chapter introduces and describes the selected objective means for field-based monitoring of physical activity in children and youth with an emphasis on their accuracy, advantages and limitations. The introduction of different instruments together with recommendations for practical application should help the reader choose the correct instrument and use it to its full potential. The second part of the chapter presents specific suggestions and recommendations for physical activity to promote an active lifestyle based on the conclusions of foreign publications, as well as the results of the authors’ own research. The proposed recommendations are of an educational and health-preventive nature. Applying these recommendations does not ‘automatically’ prevent ‘lifestyle diseases’ but substantially reduces the probability of their outbreak or worsening.

The function of adipose tissue is influenced by many factors as hormones, cytokines, but adipose tissue is active also as an endocrine organ. The amount of adipose tissue and its function is also influenced by external factors as nutrition and physical activity. The age and the stage of sexual development has to be taken into account too, and the differences between children in prepubertal, pubertal age and in adults in adipose tissue metabolism can be therefore found. The factors which influence adipose tissue’s metabolism and the factors produced by adipocytes will be also presented. All mentioned factors are influenced by external factors, specially by exercise. Acceptable work load and exercise and the adaptation to it has to be considered and applied in children as compared to the adults. Hormonal and cytokines regulation of adipose tissue can be also changed by exercise in obese subjects.

Physical fitness (PF) in children and adolescents has been declining during last decades along with physical activity (PA) level. As shown by numerous studies, the beginning, rate and rapidity of these changes has been different in various parts of the world as related to local environmental, social, economic, cultural, climatic, and other life conditions. Significant relationship of these changes to health status and prognosis was also revealed. The seriousness of this problem has been emphasized especially that it started to appear already at very early periods of life. Studies of children revealed increasing adiposity along with deteriorating motor abilities already in preschool age, when the level of PA is spontaneously highest. This goes along with earlier adiposity rebound (AR), increasing adiposity and decreasing PA level. Preschool period is defined as one of the critical stages of development, when reduction of natural activity can have more serious consequences than later on. In schoolchildren and adolescents adiposity has been also increasing, and functional capacity along with motor abilities decreasing in many coutries; positive consequences of increased PA régimes have been greater due to the possibility for more intense exercise and sport activities. Increased effort for intervention – which should be based on individual somatic and functional evaluation – should start as early as possible.

Due to health risks resulting from obesity and reduced metabolic and cardiorespiratory fitness, an increasing attention has been focusing on physical activity (PA). Its reduction - sedentarism has been considered as one of the most important causes of overweight and obesity, especially when it appears early in life. - Obesity during growth is characterized by temporarily accelerated growth in height, increased amount and changed distribution of adipose tissue (mainly on the trunk), reduced physical fitness (PF; especially aerobic, cardiorespiratory one), skill, endurance and motor development. This situation decreases even more PA, resulting in further increasing adiposity and obesity prevalence. Present or later development of metabolic syndrom, cardiovascular diseases, orthopedic and psychological problems can accompany early start of increased adiposity. Various approaches starting with a monitored diet have been suggested and elaborated for intervention, obesity treatment and prevention, with the emphasis on régimes with increased PA and special exercise. Best results with regard to BMI and fat reduction along with increased PF and reduction of metabolic disorders in specialized pediatric centers and summer camps with adequate control and guiding by physical education pedagogues and nutrition specialists have been achieved; however, positive results of these interventions have been mostly only temporary. Therefore, it is necessary to adhere to a permanent régime of both increased PA and monitored diet without interruption, which always increases adiposity and reduces PF. In such a case it is recommendable to repeat interventions more times. However, as best management of obesity during growth, an early intervention and prevention using natural factors as an optimal PA régime along with monitored adequate diet are suggested and elaborated.

Obesity develops under complex internal and environmental influences affecting child’s behavior from the beginning of postnatal life. Psychosocial factors accompanying increased body weight play the important role in forming personality of obese child, his attitudes towards world, society and to himself, as well as attitudes towards food, food choice, and eating behavior. Large scale of behavioral disturbances of the overweight children and adolescents have been reported, such as low selfesteem, depression, anxiety, shame of worse physical fitness, lower school performance, victimization from peers, withdrawal from social contacts, even lower financial evaluation. Many studies have been based on large population samples. However, many overweight and obese subjects are without behavioral problems, they don’t suffer from social victimization, they are able to cope effectively with environmental stress. The question of causality of behavioral problems of obese individuals has been discussed. Deeper insight into the characteristis of personality of individual obese child and/or adolescent may help to reveal their specific behavioral problems, if any. This may be helpful in designing effective preventive programs or therapy of obesity.