Lack of physical activity and/or physical fitness are some reasons epidemiologists suggest for increase in childhood obesity in the last 20 years, with clear correlation between body composition and physical activity and/or physical fitness yet to be determined. The objectives of the study were to (a) investigate the prevalence of overweight and obesity among Serbian school children and (b) determine the relationship between indicators of physical activity and body fatness in Serbian school children aged 6-14 years. The study subjects included a representative sample of Serbian elementary school children (n=1, 121—754 boys and 367 girls—aged 6.2-14.1 years), all of whom were recruited in the OLIMP (Obesity and Physical Activity among Serbian School Children) study. Anthropometric and physical fitness values, including body mass index (BMI), waist-circumference, body-fat, and aerobic capacity, were measured in all the children. Significant differences were found between male and female children regarding the prevalence of obesity (6.8% vs 8.2%, p<0.05, boys and girls respectively). Boys had significantly lower body mass, BMI, waist-circumference, sum of six skinfolds, and body-fat compared to their female counterparts (p<0.05). The highest level of weight, BMI, body-fat, and waist-circumference observed in a 14-year old girl (96.3 kg, 40.5 kg/m2, 54.5%, 91.4 cm respectively) implies the existence of extreme obesity in Serbian school children. The negative relationship between body-fat and maximal oxygen (VO2max) uptake was moderately high (r=-0.76; p<0.05). The study has shown a high prevalence of adiposity among Serbian school children, with a strong negative relationship between aerobic fitness and body fatness. Data of the study emphasize the necessity to identify children with weight problems and to develop early interventions to improve physical activity in children and prevent the increase of childhood obesity.

The main aim of this study was to determine the extent to which physical activity and adiposity are associated with blood cholesterol levels in male adolescents. Anthropometric and physical fitness values were measured in all children. Body mass index (BMI) and physical activity index (PAI) were used to split participants into active overweight (ACO) and non-active normal-weight (NAN) groups. The cutoffs for the ACO group were BMI ≥ 22.6 kg/m 2 and PAI ≥ 3.5, respectively, whereas the corresponding cutoffs for the NAN groups were BMI < 20.0 kg/m 2 and PAI < 2. A total of 65 children (29 in ACO group, 36 in NAN group) were selected according to above criteria. ACO group showed significantly higher BMI and body fat as compared to their NAN counterparts (p < 0.05). Adolescents from ACO group attained superior score for PAI and aerobic fitness (p < 0.05). Most blood lipid variables were significantly lower in ACO group as compared to NAN (p < 0.05) while HDL-cholesterol was higher in ACO group (p < 0.05). There was significant positive correlation between HDLcholesterol and PAI in ACO group (r = 0,38; p < 0.05). Physical activity index explained the majority of variance in HDL-cholesterol for ACO group (β = 0,513; p < 0.05). It seems that physical activity in adolescents is more important factor in balancing blood lipid status than adiposity per se, particularly for HDL-cholesterol.