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Table 2 Difference in BMI (kg/m2), waist circumference, FMI (fat mass in kg/m2) and LMI (lean mass in kg/m2) between Fit Futures 1 (2010–2011) and Fit Futures 2 (2012–2013), according to hours per week of physical activity in leisure time at baselinea

From: Longitudinal changes in body composition and waist circumference by self-reported levels of physical activity in leisure among adolescents: the Tromsø study, Fit Futures

 Beta for ∆BMI (95% CI)Beta for ∆waist circumference (95% CI)Beta for ∆FMI (95% CI)Beta for ∆LMI (95% CI)
BoysnModel 1Model 2Model 1Model 2Model 1Model 2Model 1Model 2
Baseline physical activity290Beta95% CIBeta95% CIBeta95% CIBeta95% CIBeta95% CIBeta95% CIBeta95% CIBeta95% CI
 Inactiveb890 0 0 0 0 0 0 0 
 About 0.5–1.5 h260.30− 0.54, 1.130.18− 0.65, 1.010.61−2.25, 3.470.49−2.38, 3.350.04− 0.74, 0.82− 0.02− 0.80, 0.760.30− 0.05, 0.650.26− 0.09, 0.61
 About 2 to 3 h480.12− 0.56, 0.800.12− 0.55, 0.80− 0.11− 2.43, 2.21−0.11− 2.44, 2.230.01− 0.62, 0.640.01− 0.63, 0.640.07− 0.21, 0.350.09− 0.20, 0.37
 About 4 to 6 h680.10− 0.50, 0.71− 0.09− 0.70, 0.53− 0.67− 2.74, 1.40− 0.84− 2.96, 1.270.07− 0.49, 0.64− 0.06− 0.64, 0.520.01− 0.25, 0.27− 0.05− 0.31, 0.22
 ≥ 7 h59− 0.07− 0.70, 0.57− 0.48− 1.24, 0.29− 0.98−3.16, 1.19− 2.54− 5.19, 0.12−0.30− 0.91, 0.30− 0.52− 1.25, 0.210.20− 0.08, 0.480.05− 0.28, 0.38
 P for linear trend 0.77 0.20 0.25 0.05* 0.41 0.22 0.41 0.75 
Girls
Baseline physical activity351                
 Inactivec950 0 0 0 0 0 0 0 
 About 0.5–1.5 h300.26− 0.50, 1.010.40− 0.37, 1.170.91−2.07, 3.891.29−1.76, 4.340.38− 0.31, 1.060.56− 0.13, 1.250.03− 0.25, 0.30− 0.01− 0.29, 0.27
 About 2 to 3 h800.03− 0.52, 0.570.09− 0.47, 0.640.01− 2.15, 2.170.14− 2.06, 2.330.14− 0.36, 0.630.21− 0.28, 0.71− 0.02− 0.22, 0.18− 0.03− 0.23, 0.17
 About 4 to 6 h95− 0.40− 0.93, 0.12− 0.25− 0.82, 0.32− 0.10− 2.17, 1.970.23−2.02, 2.49− 0.30− 0.78, 0.17− 0.12− 0.63, 0.39− 0.05− 0.24, 0.15− 0.08− 0.29, 0.13
 ≥ 7 h510.51− 0.12, 1.140.740.04, 1.44*2.16− 0.33, 4.642.800.02, 5.57*0.600.03, 1.18*0.900.27, 1.53*0.01− 0.22, 0.24− 0.04− 0.30, 0.22
 P for linear trend 0.69 0.34 0.23 0.15 0.48 0.14 0.88 0.60 
  1. *Significantly different from the reference (p < 0.05)
  2. aModel 1 adjusted for baseline measurement of outcome. Model 2 adjusted for baseline measurement of outcome, screen time on weekdays, regularity of eating breakfast, age in half years at baseline and days between measurements
  3. bInactive boys had a mean increase of 1.1 BMI units, 3.2 cm waist circumference, 0.6 FMI units and 0.3 LMI units
  4. cInactive girls had a mean increase of 0.8 BMI units, 0.6 cm waist circumference, 0.5 FMI units and 0.1 LMI units