Ha, Yook, and Lee: Effects of 16-Week Exercise on Insulin, HOMA-IR, and Glucose Levels in Obese Childhood
Abstract
PURPOSE
This study aimed to evaluate the effects of a 16-week exercise program on insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and glucose levels. This study aimed to assess whether regular physical activity could improve insulin sensitivity and reduce metabolic risk, particularly in children with obesity.
METHODS
Thirty-three elementary school students aged 11-12 years were recruited, 16 of whom were classified as having normal weight and 17 with obesity, based on body mass index percentiles. The participants engaged in a structured exercise program for 16 weeks, which included sports games, aerobic exercises, and resistance training, performed three times per week. Fasting insulin, glucose, and HOMA-IR levels were measured before and after the intervention.
RESULTS
At baseline, the obese group exhibited significantly higher insulin and HOMA-IR levels, compared with the normal-weight group. After the 16-week exercise program, the obese group showed a significant reduction in both insulin and HOMA-IR levels, indicating improved insulin sensitivity. No significant changes in the glucose levels were observed in either group. The normal-weight group did not show significant changes in insulin or HOMA-IR levels after the intervention.
CONCLUSIONS
The findings suggest that a 16-week structured exercise program can significantly improve insulin sensitivity in children with obesity, as evidenced by reductions in insulin and HOMA-IR levels. These results highlight the importance of incorporating regular physical activity into interventions aimed at managing obesity and its associated metabolic risks in children.
Keywords: Obesity, Exercise, Insulin, HOMA-IR, Glucose, Childhood
INTRODUCTION
Childhood obesity is a growing global epidemic with profound implications for both physical and metabolic health [ 1]. Obese children are at an increased risk of developing insulin resistance, a condition in which the body’s cells become less responsive to insulin, leading to higher levels of circulating insulin [ 2]. Insulin resistance is a precursor to more serious conditions, such as type 2 diabetes and metabolic syndrome, making it a critical area of concern for pediatric health [ 3]. Early intervention is essential to mitigate these risks, with exercise identified as a key factor in improving insulin sensitivity and overall metabolic health.
Insulin resistance is commonly assessed using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), which estimates insulin sensitivity based on fasting insulin and glucose levels [ 4]. Elevated HOMA-IR scores indicate higher insulin resistance, a condition fre-quently observed in obese children compared to their normal-weight peers [ 5]. This relationship between obesity and insulin resistance underscores the importance of addressing these metabolic imbalances early, particularly through lifestyle interventions such as diet and exercise.
Exercise is widely recognized as an effective intervention for improving insulin sensitivity and reducing the risk of metabolic diseases [ 6]. Regular physical activity has been shown to decrease insulin levels, lower HOMA-IR scores, and improve glucose metabolism, particularly in obese individuals [ 7]. Beyond insulin sensitivity, exercise also confers benefits to cardiovascular health, muscular strength, and overall well-being [ 8]. However, the specific effects of structured exercise programs on insulin, HOMA-IR, and glucose levels in obese children.
Given the rising prevalence of obesity and its associated metabolic risks among children, it is crucial to develop effective exercise interventions tailored to this population. Understanding the impact of different exercise modalities on metabolic markers such as insulin and HOMA-IR in obese children is essential for designing targeted strategies to prevent and manage obesity-related complications. This study aims to investigate the effects of a 16-week structured exercise program (EP) on insulin, HOMA-IR, and glucose levels in obese and normal-weight ele-mentary school students. By comparing the pre- and post-intervention data, this research to provide insights into the effectiveness of exercise in improving metabolic health.
METHODS
1. Participants and Procedure
Thirty-three elementary school students aged 11-12 years (mean age 11.42±1.12 years, all male) participated in this study. Participants were categorized into two groups based on BMI (body mass index) using age- and gender-specific cut-off values [ 9]; a non-obesity group (BMI: 18 to 24, n=17) and an obesity group (BMI: 25 to 32, n=16). The health status of participants was assessed through a health questionnaire, physical ex-amination, and laboratory tests. To minimize potential diurnal variations, all measurements were conducted at 08:00 AM. Body composition and blood samples were measured using the standardized methods under consistent conditions.
The measurements were performed twice, once before and once after the 16-week intervention, following the procedures recommended by the American College of Sports Medicine (ACSM). Participants’ demo-graphic and physiological characteristics, including height, weight, body fat percentage (BFP), and BMI, are presented in Table 1. Prior to participation, all subjects were informed of the potential risks and discomforts associated with the study. Written informed consent was obtained from all participants, with approval from the Institutional Human Research Committee, in accordance with the ethical standards of the Helsinki Declaration (DUIRB-202206-18) (WS-2020-13).
Table 1.
Body composition of two groups before and after the 16-weeks exercise program
Variables |
Groups |
Pre-EP (mean±SD) |
Post-EP (mean±SD) |
Effect size Cohen’s d
|
Interaction |
Main effect |
Height (cm) |
Non-obesity |
144.55±9.94 |
147.78±9.05***
|
0.36 ( small) |
F=3.445, |
Time F=139.157, |
|
Obesity |
148.44±7.53 |
152.88±7.33***
|
0.59 ( medium)
|
p=.073 |
††† p=.000 |
|
Difference
|
2.69±8.63% |
3.45±7.88% |
0.09 ( no effect) |
|
|
Weight (kg) |
Non-obesity |
45.31±7.02 |
46.94±7.09 |
0.23 ( small) |
F=0.519, |
Group F=26.132, |
|
Obesity |
58.57±6.93 |
59.31±8.55 |
0.11 ( no effect) |
p=.477 |
††† p=.000 |
|
Difference
|
29.3±22.2% |
26.3±24.0% |
-0.14 ( no effect) |
|
|
BMI (kg/m2) |
Non-obesity |
21.62±1.91 |
21.39±1.67 |
-0.12 ( no effect) |
F=1.538, |
Group F=50.291, |
|
Obesity |
26.54±1.61 |
25.56±2.76 |
-0.61 ( medium) |
p=.224 |
††† p=.000 |
|
Difference
|
22.8±11.7% |
19.5±15.2% |
-0.28 ( small) |
|
|
BFP (%) |
Non-obesity |
30.33±6.23 |
29.08±7.38 |
-0.20 ( small) |
F=12.800 |
Time F=23.200, |
|
Obesity |
37.61±8.01 |
29.16±5.77***
|
-1.06 ( large) |
††† p=.001 |
††† p=.000 |
|
Difference
|
24.0±33.8% |
0.28±32.2% |
-0.70 ( large) |
|
|
2. Exercise program
The exercise program (EP) was adapted for a structured and supervised after-school intervention, based on the exercise prescription program presented by the ACSM [ 10]. The program was conducted three times per week over a two-week adjustment period. Each session lasted for 60 minutes, including a 5-minute warm-up, a 50-minute main exercise period (comprising sports game, aerobic exercise, and resistance training), and a 5-minute cool-down. The intensity of EP was progres-sively increased: 50-60% of HRR/11-12 of RPE during weeks 1-4, to 60-70% of HRR/12-13 RPE during weeks 5-13, and 70-80% of HRR/13-14 RPE during weeks 14-16. Heart rate monitors (V800, Polar Electro, Oy, Kempele, Finland) were used throughout each training session to ensure participants maintained the appropriate intensity. All sessions were fully supervised by the researchers.
3. Body composition
Body weight (kg) and BFP (%) were assessed using the Inbody J10 device (Biospace Corp., Seoul, Korea), which operated on the principle of bioelectrical impedance. BMI (kg/m2) was calculated using the formula: weight (kg) divided by height (m2).
4. Blood sampling and Blood sample analysis
To investigate the potential effects of the exercise intervention, blood samples were obtained from all participants at baseline and after 16 weeks. Participants were instructed to fast for a minimum of 8 hours prior to each sample collection. Between 8:00 AM and 10:00 AM, a clinical pathologist collected 10 mL of blood from the antecubital vein. The samples were centrifuged at 3,500 g for 15 minutes at 4°C, and the serum was then separated and stored at -80°C until conducting the analysis. Fasting plasma glucose levels (mg/dL) were measured using enzy-matic methods with a Hitachi Modular D2400 automated chemistry analyzer (Hitachi, Tokyo, Japan). Fasting insulin concentrations (μU/mL) were determined using a chemiluminescent microparticle immunoassay (Abbott Architect system, Irving, TX, USA). Insulin resistance was calculated using the homeostatic model assessment of insulin resistance (HOMA-IR) with the formula: HOMA-IR=(fasting blood glucose [mg/dL]×insulin [μU/mL])/405 [ 11].
5. Statistical analysis
An a priori power analysis was conducted using G*Power 3.1 to determine the required sample size for the study. The optimal total sample size was calculated to be N=36, assuming a small effect size of F=0.25 (default), a power of 0.80, and an alpha of 0.05 was calculated. All statistical tests were performed with an alpha level of p <.05. A two-way analysis of variance with repeated measures was used to compare pre- and post-exercise changes within and between groups, with post hoc analysis conducted using Bonferroni’s test. If no significant interaction was found, main effects of time and group were analyzed. Additionally, effect sizes (Cohen’s d) were calculated to assess pre- and post- intervention data. Pearson’s correlation coefficients were used to evaluate the associations between changes in body composition and blood biomarkers. The inclusion and exclusion criteria for these analyses were based on the significance level of the F-value, set at 0.05. The best equation was selected based on the highest multiple correlation coefficient (R2).
RESULTS
1. Exercise regulated the balance of body compositions in childhood obesity
Prior the exercise program (EP), we assessed the body compositions of participants in both the non-obesity and obesity groups, including height, weight, BMI, and BFP ( Table 1). Initial comparisons revealed that height was similar between the two groups, with a difference of only 2.69%. However, body weight, BMI, and BFP were significantly higher in the obese group by 29.3%, 22.8%, and 24.0% respectively (all p <.001). Following the EP, there were no significant changes in height, weight, or BMI within or between the groups, with differences remaining consistent pre- and post-EP. Notably, the difference in BFP between the groups significantly decreased from 24.0% pre-EP to 0.28% post-EP (Interaction: p =.001; main effect of time: p <.001). Additionally, the effect size of the EP on BMI (d=-0.61) and BFP (d=-1.06) was greater in the obese group compared to the non-obese group.
2. Exercise recovered insulin resistance of childhood obesity
To evaluate the effects of the EP on glucose homeostasis and insulin resistance, we measured serum glucose and insulin levels, as well as HOMA-IR scores in both groups before and after the intervention. At baseline, the obese group exhibited significantly higher insulin levels (main effect of group: p =.012) and HOMA-IR scores (main effect of group: p =.015) compared to the non-obese group ( Fig. 1 and Table 2). There was no significant group effect on glucose levels. After the EP, both insulin levels (main effect of time; p =.001) and HOMA-IR scores (main effect of time; p =.004) significantly decreased in the obesity group, with no significant changes observed in the non-obese group. The effect size (Cohen’s d) for changes in insulin, glucose, and HOMA-IR score were small for both groups (d=0.10-0.38; Table 2).
Fig. 1.
Fig. 1.Changes in HOMA-IR scores and glucose and insulin levels after the exercise. (A) The 16-week EP did not affect glucose levels in both the non-obesity and obesity groups. (B, C) Repeated measures two-way ANOVA showed that the obesity group was higher insulin levels and HOMA-IR scores than those in the non-obesity group († p<.05). A post hoc Bonferroni's test showed the EP significantly decreased insulin levels (*** p<.001) and HOMA-IR scores (* p<.05) in the obesity group. All values are presented as mean±standard deviation (SD) (n=17 for the non-obesity group; n=16 for the obesity group). * p<.05 and *** p<.001 vs. Pre-EP; † p<.05, non-obesity group vs. obesity group.
Table 2.
Change of insulin resistance after 16 weeks of the exercise program
|
Group |
Pre-EP Mean±SD |
Post-EP Mean±SD |
Effect size Cohen’s d
|
Interaction |
Main effect |
Glucose (mg/dL) |
Non-obesity |
86.82±8.37 |
87.65±9.14 |
-0.23 |
p=.519 |
† Time p=.018 |
|
Obesity |
90.31±10.70 |
89.06±11.13 |
-0.38 |
|
|
Insulin (μU/mL) |
Non-obesity |
27.65±11.16 |
25.10±10.82 |
0.10 |
† p=.021 |
†† Time p=.001 |
|
Obesity |
50.27±29.54 |
38.97±23.85***
|
-0.12 |
|
† Group p=.012 |
HOMA-IR |
Non-obesity |
6.02±2.71 |
5.37±2.24 |
-0.24 |
† p=.050 |
†† Time p=.004 |
|
Obesity |
11.74±8.47 |
8.73±5.76*
|
-0.36 |
|
† Group p=.015 |
3. Insulin correlated with changes of body composition and HOMA-IR following exercise
To explore the relationship between biochemical markers and the EP-improved improvements insulin levels and body composition level, we conducted correlations analyses using the delta values (difference) of all parameters pre- and post-EP. Although no significant correlation was observed between insulin levels and body composition in either group (r=0.398, p =.022; Fig. 2B), a significant association was found between decreased C-peptide levels and increased HOMA-IR in the obese group (r=0.899, p <.001; Fig. 2A).
Fig. 2.
Fig. 2.Correlation between change in Insulin at HOMA-IR and BFP levels after exercise intervention. (A) The change (Δ) Insulin was correlated with the change (Δ) of HOMA-IR (r=0.899, p<.001) and (B) BFP (r=0.398, p=.022) after the intervention of exercise program (EP) in non-obesity and obesity group. Correlation analysis was performed Pearson's correlation coefficients. Each gray and back circle represents an individual subject of non-obesity (n=17) and obesity (n=16), respectively.
To explore the relationship between biochemical markers and the EP-induced improvements in insulin levels and body composition, we conducted correlation analyses using the delta values (differences) of all parameters pre- and post-EP. Although no significant correlation was observed between insulin levels and body composition in either group (r=0.190, p =.022; Fig. 2B), a significant association was found between decreased C-peptide levels and increased HOMA-IR in the obese group (r=0.899, p <.001; Fig. 2A).
DISCUSSION
This study aimed to evaluate the effects of a 16-week exercise program on insulin, HOMA-IR, and glucose levels in normal-weight and obese elementary school students. Our findings indicate that the exercise intervention significantly reduced insulin levels and HOMA-IR in the obese group, suggesting an improvement in insulin sensitivity. However, no significant changes were observed in glucose levels in either group. These results support with previous studies demonstrating the beneficial effects of physical activity on insulin sensitivity, particularly in populations with higher levels of adiposity and metabolic risk.
The reduction in insulin and HOMA-IR observed in the obese group is consistent with findings from similar studies. For instance, a previous study reported significant reductions in insulin levels and HOMA-IR in overweight children following a 12-week exercise program [ 12]. Similarly, obese adolescents who participated in a structured exercise regimen showed improved insulin sensitivity, as indicated by lower HOMA-IR scores [ 13]. Exercise may enhance insulin sensitivity without significantly altering glucose levels, as glucose homeostasis is tightly regulated by the body’s compensatory mechanisms even in insulin-resistant individuals [ 14]. These studies support the notion that regular physical activity is an effective intervention for improving metabolic health in obese youth.
Interestingly, the current study did not find significant changes in glucose levels in either the normal-weight or obese group, despite improvements in insulin sensitivity. This outcome is consistent with findings from several other studies that also reported stable glucose levels despite reductions in insulin and HOMA-IR following an exercise intervention [ 15]. The lack of significant change in glucose levels could also be attributed to the relatively short duration of the intervention and the participants’ baseline metabolic status [ 16]. The stability of glucose levels may result from the body’s ability to maintain glucose homeostasis even as insulin sensitivity improves. This suggests that while exercise enhances the efficiency of insulin, it does not necessarily alter fasting glucose levels in a short-term intervention.
The exercise program implemented in this study included a combination of aerobic and resistance training, both of which have been shown to be effective in improving metabolic outcomes. Aerobic exercise is known to enhance cardiovascular fitness and increase the body’s capacity to utilize glucose, while resistance training improves muscle mass and insulin sensitivity [ 17, 18]. Previous studies have demonstrated that combined exercise modalities are more effective than either type alone in reducing insulin resistance and improving metabolic health [ 19, 20]. The results of this study support the efficacy of such a combined approach, particularly for obese children who may benefit from the multifaceted effects of both aerobic and resistance training.
The significant reduction in insulin and HOMA-IR in the obese group underscores the potential of exercise as a key component in managing and preventing insulin resistance and type 2 diabetes in obese children [ 21]. The findings are particularly relevant given the increasing prevalence of childhood obesity and its associated metabolic complications. The study highlights the importance of early intervention through physical activity to mitigate the long-term health risks associated with obesity [ 22]. The lack of significant changes in the normal-weight group suggests that while exercise is beneficial for all children, its impact on insulin sensitivity is more pronounced in those who already exhibit some degree of metabolic dysfunction.
The strong correlation between insulin levels and HOMA-IR following the 16-week exercise program underscores the close relationship between these two markers in assessing insulin sensitivity. Since HOMA-IR is derived from fasting insulin and glucose levels, the observed reductions in insulin were directly reflected in lower HOMA-IR scores, high-lighting the impact of exercise on improving insulin sensitivity [ 23]. This correlation reinforces the importance of monitoring both insulin and HOMA-IR to evaluate the effectiveness of exercise interventions in reducing insulin resistance, particularly in at-risk populations.
Despite the promising findings, this study has several limitations. The relatively small sample size and the duration of the intervention may limit the generalizability of the results. Additionally, the potential impact of maturity on our findings and recognized, and the future studies should incorporate importance assessments of maturity to provide a more comprehensive understanding of the effects of exercise on metabolic outcomes in this age group. Furthermore, the study did not control for dietary intake, which could have influenced the outcomes. Future research should address these limitations by including larger sample sizes, longer intervention periods, maturity and controlled dietary assessments. Moreover, exploring the long-term effects of exercise on insulin sensitivity and glucose metabolism, as well as the potential benefits of varying the type, intensity, and duration of exercise interventions, would be beneficial.
CONCLUSION
This study provides compelling evidence that a 16-week structured exercise program can significantly enhance insulin sensitivity in obese elementary school children, as indicated by reductions in insulin and HOMA-IR levels. These findings underscore the critical importance of integrating regular physical activity into interventions designed to manage and prevent obesity-related metabolic disorders in children. Furthermore, the results offer valuable insights into the role of exercise as a foundational element in combating childhood obesity and its associated health risks. Given the growing prevalence of childhood obesity, future research should focus on identifying the most effective types, intensities, and durations of exercise to optimize metabolic health in this vulnerable population. Additionally, exploring the long-term sustainability of these benefits and the potential interactions between exercise, diet, and other lifestyle factors will be essential in developing comprehensive strategies to address pediatric obesity and its complications.
REFERENCES
2. Fang Z, Zhu L, Chen Y, Jin Y, Yao Y. Elevated remnant cholesterol was associated with the increased metabolically unhealthy obesity risk in Chinese youth. Asia Pac J Clin Nutr. 2024;33(3):389-96.
3. Greene RK, Gangidi S, Zhao R, Nelson JM, Harms K, et al. The relationship between acrochordons, obesity, and metabolic syndrome in the pediatric population: a retrospective cohort study. Pediatr Dermatol. 2024;41(4):660-6.
4. Janchevska A, Gucev Z, Tasic V, Polenakovic M. Homeostasis Model Assessment - Insulin Resistance and Sensitivity (HOMA-IR and IS) Index in Overweight Children Born Small for Gestational Age (SGA). Pril (Makedon Akad Nauk Umet Odd Med Nauki). 2018;39(1):83-9.
5. Tascilar ME, Cekmez F, Meral C, Pirgon O, Tanju IA, et al. Evaluation of adipocytokines in obese children with insulin resistance. Turk J Pediatr. 2011;53(3):269-73.
6. Tan JTM, Price KJ, Fanshaw SR, Bilu C, Pham QT, et al. Exercise reduces glucose intolerance, cardiac inflammation and adipose tissue dysfunction in psammomys obesus exposed to short photoperiod and high energy diet. Int J Mol Sci. 2024;25(14).
7. MacDonald-Ramos K, Monroy A, Bobadilla-Bravo M, Cerbon M. Si-lymarin reduced insulin resistance in non-diabetic women with obesity. Int J Mol Sci. 2024;25(4).
8. Tremblay EJ, Peyrel P, Karelis AD, Rabasa-Lhoret R, Tchernof A, et al. Resistance training and cardiometabolic risk in women with metabolically healthy and unhealthy obesity. Appl Physiol Nutr Metab. 2024;49(8):1068-82.
9. Obesity: preventing and managing the global epidemic. Report of a WHO consultation. World Health Organ Tech Rep Ser. 2000;894:i-xii. 1-253.
10. Thompson PD, Arena R, Riebe D, Pescatello LS; American College of Sports M. ACSM's new preparticipation health screening recommendations from ACSM's guidelines for exercise testing and prescription, ninth edition. Curr Sports Med Rep. 2013;12(4):215-7.
11. Gunes O, Tascilar E, Sertoglu E, Tas A, Serdar MA, et al. Associations between erythrocyte membrane fatty acid compositions and insulin resistance in obese adolescents. Chem Phys Lipids. 2014;184:69-75.
12. Nassis GP, Papantakou K, Skenderi K, Triandafillopoulou M, Kavouras SA, et al. Aerobic exercise training improves insulin sensitivity without changes in body weight, body fat, adiponectin, and inflammatory markers in overweight and obese girls. Metabolism. 2005;54(11):1472-9.
14. Boule NG, Weisnagel SJ, Lakka TA, Tremblay A, Bergman RN, et al. Effects of exercise training on glucose homeostasis: the HERITAGE Family Study. Diabetes Care. 2005;28(1):108-14.
15. Silva FM, Duarte-Mendes P, Ferreira JP, Carvalho E, Monteiro D, et al. Changes in metabolic and inflammatory markers after a combined exercise program in workers: a randomized controlled trial. Med Sci Sports Exerc. 2024;doi: 10.1249/MSS.0000000000003510.
19. Pataky MW, Kumar AP, Gaul DA, Moore SG, Dasari S, et al. Diver-gent skeletal muscle metabolomic signatures of different exercise training modes independently predict cardiometabolic risk factors. Diabetes. 2024;73(1):23-37.
20. Gil-Cosano JJ, Plaza-Florido A, Gracia-Marco L, Migueles JH, Cadenas-Sanchez C, et al. Effects of combined aerobic and resistance training on the inflammatory profile of children with overweight/obesity: a randomized clinical trial. Pediatr Obes. 2024.
21. Nikseresht M, Dabidi Roshan V, Nasiri K. Inflammatory markers and noncoding-RNAs responses to low and high compressions of HIIT with or without berberine supplementation in middle-aged men with prediabetes. Physiol Rep. 2024;12(15):e16146.
23. Delanghe JR, Verlinde E, Speeckaert MM, Maenhout T. HOMA-IR and HOMA2-IR estimation based on glycated hemoglobin as an alternative for fasting glucose. Acta Clin Belg. 2023;78(4):308-12.
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