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Table 2 Comparisons of characteristics between the normal weight and underweight groups in boys (Japan, 2001–2008)

From: Lifestyle factors associated with underweight among Japanese adolescents: a cross-sectional study

  Normal weight (n = 933) Underweight (n = 99) P valuea
Age (years) 12.0 (12.0, 13.0) 12.0 (12.0, 13.0) 0.186
Birthweight (g), n (%)
  < 2500 50 (5.4) 10 (10.1) 0.055
  ≥ 2500 883 (94.6) 89 (89.9)  
Height (cm) 155.5 (149.2, 160.8) 149.9 (144.6, 154.7) <0.001
Weight (kg) 43.7 (39.1, 48.3) 33.0 (30.8, 36.2) <0.001
Body mass index (kg/m2) 18.0 (16.9, 19.2) 15.0 (14.6, 15.3) <0.001
Exercise, n (%)
 Daily 788 (84.5) 81 (81.8) 0.325
 Sometimes 71 (7.6) 6 (6.1)  
 None 74 (7.9) 12 (12.1)  
Skipping breakfast, n (%)
 Yes 45 (4.8) 3 (3.0) 0.421
 No 888 (95.2) 96 (97.0)  
Snacking after dinner, n (%)
 Always or often 580 (62.2) 57 (57.6) 0.372
 Seldom or none 353 (37.8) 42 (42.4)  
Snacking while watching television or reading books, n (%)
 Yes 383 (41.1) 34 (34.3) 0.196
 No 550 (59.0) 65 (65.7)  
Eating slowly, n (%)
 Yes 161 (17.3) 35 (35.4) <0.001
 No 772 (82.7) 64 (64.7)  
  1. Except where indicated n (%), values are expressed as median (25, 75th percentile)
  2. aWilcoxon rank-sum test or chi-square test