Published online Jul 15, 2023. doi: 10.4239/wjd.v14.i7.1126
Peer-review started: April 17, 2023
First decision: May 15, 2023
Revised: May 22, 2023
Accepted: June 2, 2023
Article in press: June 2, 2023
Published online: July 15, 2023
Processing time: 86 Days and 23.9 Hours
The global obesity epidemic, not sparing children and adolescents, is accompanied by rapid increase in the prevalence of cardiometabolic disorders. The association between obesity and insulin resistance is well established, along with the fact that insulin resistance represents a pivotal step in the progression towards prediabetes and type 2 diabetes. Obese adolescents who are in puberty should be regarded as a particularly vulnerable group for glucose metabolism dysregulation. Growing evidence supports the notion that young-onset type 2 diabetes has a more aggressive disease phenotype, leading to early development of complications, and adversely affecting quality of life and long-term outcomes. As more than half of the world’s population is expected to be overweight or obese within the next decade, expanding the options to manage adolescent obesity is essential to treat the epidemic.
Cardiorespiratory fitness (CRF), referring to ability of the circulatory and respiratory systems to supply oxygen to skeletal muscle mitochondria for energy production during sustained physical activity has been associated with the insulin resistance, irrespective of body weight. In children and adolescents, CRF is an important marker of health which shows an inverse relationship with obesity, insulin resistance and cardiometabolic risk. Available data confirm that association between fatness and cardiometabolic risk scores could be partially decreased with improvements in fitness levels. It seems that early intervention and prevention strategies targeting youth CRF may be associated with reduced risk for obesity and cardiometabolic disease later in life.
To investigate the association between CRF and insulin resistance in obese adolescents, with special emphasis on severely obese adolescents.
This was a prospective, cross-sectional study including 200 pubertal adolescents, 10 years to 18 years of age. According to body mass index (BMI), adolescents were classified as mildly obese (BMI 100% to 120% of the 95th percentile for age and sex) or severely obese (BMI ≥ 120% of the 95th percentile for age and sex or ≥ 35 kg/m2, whichever was lower). Participant body composition was assessed by bioelectrical impedance analysis (BIA). A homeostatic model assessment of insulin resistance (HOMA-IR) was calculated. Maximal oxygen uptake (VO2max) was determined from submaximal treadmill exercise test. CRF was expressed as VO2max scaled by total body weight (mL/min/kg TBW) or by fat free mass (mL/min/kg FFM), and then categorized as poor, intermediate or good, according to VO2max terciles. Data were analyzed by statistical software package SPSS (IBM SPSS Statistics for Windows, Version 24.0). P value < 0.05 was considered statistically significant.
We observed a weak negative correlation between CRF and HOMA-IR [Spearman’s rank correlation coefficient (rs) = -0.28, P < 0.01 for CRFTBW; (rs) =-0.21, P < 0.01 for CRFFFM]. A one-way analysis of variance (ANOVA) revealed a significant main effect of CRF on HOMA-IR [F(2200) = 6.840, P = 0.001 for CRFTBW; F(2200) = 3.883, P = 0.022 for CRFFFM]. Subsequent analyses showed that obese adolescents with poor CRF had higher HOMA-IR than obese adolescents with good CRF (P = 0.001 for CRFTBW; P = 0.018 for CRFFFM). Two-way ANOVA with Bonferroni correction confirmed significant effect of interaction of CRF level and obesity category on HOMA-IR [F(2200) = 3.292, P = 0.039 for CRFTBW]. Severely obese adolescents had higher HOMA-IR than mildly obese, with either good or poor CRF. However, HOMA-IR did not differ between severely obese adolescents with good and mildly obese adolescents with poor CRF.
CRF is important determinant of insulin resistance in obese adolescents, regardless of obesity category. Therefore, CRF assessment should be a part of diagnostic procedure, and its’ improvement should be a therapeutic goal.
Large scale prospective studies are needed to expand the knowledge of CRF, IR, and cardiometabolic health. Also, determination of participants’ body composition by using different methods (such as abdominal MR scans) would offer more precise insight into type and distribution of body fat.