Association between cardiorespiratory fitness level and insulin resistance in adolescents with various obesity categories

Table 1 Distribution of adolescents according to puberty stage and obesity category, n (%)

Variable	All	Females	Males	1P value
Tanner stage				< 0.001
II	33 (16.5)	7 (5.8)	26 (32.9)
III	22 (11.0)	9 (7.4)	13 (16.5)
IV	41 (20.5)	21 (17.4)	20 (25.3)
V	104 (52.0)	84 (69.4)	20 (25.3)
Obesity category				0.004
Class I	71 (35.5)	54 (44.6)	17 (21.5)
Class II	79 (39.5)	42 (34.7)	37 (46.8)
Class III	50 (25.0)	25 (20.7)	25 (31.6)

¹χ² test.

Table 2 Anthropometric characteristics, maximal oxygen uptake, fasting glucose, fasting insulin, and homeostatic model assessment of insulin resistance in adolescents with different obesity classes, mean ± SD

Variable	Class I obesity, n = 71 (35.5%)	Class II obesity, n = 79 (39.5%)	Class III obesity, n = 50 (25.0%)	1P
Height, cm	166.65 ± 9.49	168.11 ± 10.10	167.32 ± 8.64	0.646
Weight, kg	88.51 ± 15.29	99.38 ± 18.59	106.52 ± 16.64	< 0.001
WC, cm	102.42 ± 10.05	107.00 ± 16.82	110.39 ± 18.37	0.017
WC/height	0.61 ± 0.05	0.64 ± 0.10	0.66 ± 0.11	0.019
BMI, kg/m2	30.65 ± 2.29	34.34 ± 2.54	41.02 ± 4.44	< 0.001
BMI z-score	1.97 ± 0.19	2.35 ± 0.15	2.68 ± 0.24	< 0.001
VO2max, L/min	2.55 ± 0.44	2.66 ± 20.54	2.77 ± 0.53	0.064
VO2max, mL/min/kg TBW	29.68 ± 3.53	27.69 ± 3.83	23.95 ± 3.60	< 0.001
VO2max, mL/min/kg FFM	46.48 ± 4.46	45.38 ± 5.90	43.63 ± 6.71	0.003
Fasting glucose, mmol/L	4.99 ± 0.41	4.99 ± 0.47	5.05 ± 0.38	0.708
Fasting insulin, mU/L	25.00 ± 12.80	28.45 ± 16.22	37.31 ± 21.11	< 0.001
HOMA-IR	5.78 ± 3.09	6.31 ± 3.68	8.49 ± 5.23	0.001

¹ANOVA/Kruskal-Wallis, Scheffe post hoc test.

BMI: Body mass index; FFM: Fat free mass; HOMA-IR: Homeostatic model assessment of insulin resistance; SD: Standard deviation; TBW: Total body weight; VO₂max: Maximal oxygen uptake; WC: Waist circumference.

Table 3 Association of cardiorespiratory fitness level scaled by total body weight and obesity category with homeostatic model assessment of insulin resistance

CRF level	Mildly obese			Severely obese			F	P
	Mean	SD	n	Mean	SD	n
Poor CRFTBW	6.12	2.97	8	8.51	5.36	58	Main effect CRFTBW, F (2200) = 1.249	0.289
Intermediate CRFTBW	7.18	3.67	26	5.82	3.04	42	Main effect obesity, F (2200) = 1.746	0.188
Good CRFTBW	4.72	2.23	37	6.37	3.41	29	Interaction CRFTBW and obesity, F (2200) = 3.292	0.039

CRF_TBW: Cardiorespiratory fitness scaled by total body weight; SD: Standard deviation.

Table 4 Association of cardiorespiratory fitness level scaled by fat free mass and obesity category with homeostatic model assessment of insulin resistance

CRF level	Mildly obese			Severely obese			F	P
	Mean	SD	n	Mean	SD	n
Poor CRFFFM	7.35	3.20	13	7.91	5.65	54	Main effect CRFFFM, F (2200) = 2.027	0.135
Intermediate CRFFFM	6.12	3.77	30	7.04	3.23	37	Main effect obesity, F (2200) = 3.846	0.051
Good CRFFFM	4.68	1.58	28	6.19	3.33	38	Interaction CRFFFM and obesity, F (2200) = 0.167	0.846

CRF_FFM: Cardiorespiratory fitness scaled by fat free mass; SD: Standard deviation.