Physical Activity Level Assessed by Accelerometer and PAQ-C in Tunisian Children.

BACKGROUND: Physical activity (PA) is an important agent in the prevention of chronic diseases such as obesity. OBJECTIVES: To provide preliminary data on PA among school children and to correlate the PA with weight status. MATERIAL AND METHODS: A total of 40 children aged between 8 and 11 years and attending Tunisian schools were recruited. The body composition was determined by using the deuterium oxide dilution technique. PA was determined by the PAQ-C (PA Questionnaire for Older Children). An objective monitoring of PA and sedentary time was achieved by using ActiGraph GT3X + accelerometers. RESULTS: PAQ-C data demonstrate that 20% of the sample had light PA levels and 80% had moderate PA levels. Times spent in sedentary (62.37%) and light (30.80%) activities were higher than that spent in moderate and vigorous (6.83%) activities. Furthermore, almost half of the sample spent more than 60 min per day in moderate-to-vigorous intensity PA (MVPA). The average MVPA was significantly higher in normal weight than overweight and obese groups (67.68 ± 20.98 vs. 49.07 ± 19.09, p = 0.007). The proportion of overweight children who spent more than 60 min per day in MVPA was significantly higher than that of normal-weight (60.9 vs. 29.4%; p = 0.049). CONCLUSION: This study indicates that half of school children comply with the health-based guidelines for PA and sedentary behavior. Our findings also suggest that obesity was associated with decrease in PA in Tunisian children.

Development and validation of impedance-based equations for the prediction of total body water and fat-free mass in children aged 8-11 years.

BACKGROUND/OBJECTIVES: Accuracy of impedance analysis depends on population-specific prediction equations. The aim of this study was to propose new prediction equations to estimate body composition using impedance analysis for healthy Tunisian children and validate them using the deuterium oxide dilution (D2O) technique. SUBJECTS/METHODS: Body composition was estimated by the Tanita impedance analyzer. The validity of this system was investigated in 134 school children aged between 8 and 11 years. The validity of other published equations was also tested in our sample. Total body water (TBW) and Fat-Free Mass (FFM) were determined using the D2O technique. Participants were divided equally into development (n = 67) and validation groups (n = 67) to develop prediction equation using linear regression models. RESULTS: The comparison between body composition obtained by Tanita system and by D2O technique illustrated a significant difference (p < 0.01). Compared to D2O technique, Tanita impedance analysis underestimates fat mass and overestimates FFM and TBW. The prediction equations for TBW and FFM were developed with sex, age, weight and resistance index as possible predictor variables. The selected equations presented the highest adjusted coefficient of determination (R2), the lowest standard error of the estimate (SEE) value and the lowest p-values. The pure error was 1.263 for the TBW equation and 1.646 for the FFM. The Bland Altman plot illustrated the good level of concordance between the TBW and FFM predicted by the new equations and measured by isotope dilution. CONCLUSIONS: Our study provides valid prediction equations for estimation of TBW, FFM from impedance analysis measures for Tunisian children. These equations are applicable to children aged between 8 and 11 years.