Table 1 Baseline characteristics of participants by BMI status at follow-up after 4 years

Sex ^{a c}

< 0.0001

 Female ( n  = 8350)

385 (31.1)

6685 (49.5)

971 (34.0)

309 (24.3)

 Male ( n  = 10,513)

852 (68.9)

6812 (50.5)

1886 (66.0)

963 (75.7)

Baseline Age in years ^d

6.76 (0.62)

6.80 (0.74)

6.78 (0.70)

6.56 (0.64)

< 0.0001

Baseline BMI z-score ^d

-0.53 (1.46)

0.06 (1.07)

0.75 (1.25)

1.12 (1.51)

< 0.0001

Baseline Weight Status

 Underweight ^c ( n  = 752)

188 (15.2)

492 (3.6)

56 (2.0)

16 (1.3)

< 0.0001

 Normal ^c ( n  = 14,804)

953 (77.0)

11,411 (84.5)

1782 (62.4)

658 (51.7)

< 0.0001

 Overweight (but not obese) ^c ( n  = 2214)

43 (3.5)

1230 (9.1)

729 (25.5)

212 (16.7)

< 0.0001

 Obese ^c ( n  = 1093)

53 (4.3)

364 (2.7)

290 (10.2)

386 (30.3)

< 0.0001

 Baseline Fitness Test Overall z-score ^bd

0.14 (0.58)

0.11 (0.64)

0.11 (0.62)

0.05 (0.63)

< 0.0001

Baseline Fitness Test z-score

 Grip strength ^d

0.05 (1.09)

0.15 (1.00)

0.41 (1.11)

0.25 (1.12)

< 0.0001

 Sit-up ^d

0.05 (1.12)

-0.03 (1.12)

-0.20 (1.21)

-0.32 (1.30)

< 0.0001

 Sit and reach ^d

-0.11 (1.02)

-0.10 (1.09)

-0.37 (1.42)

-0.46 (1.54)

< 0.0001

 Endurance run ^d

0.55 (0.84)

0.36 (0.99)

0.17 (0.90)

0.18 (0.84)

< 0.0001