Extended Abstract

1. Introduction and Purpose

Abdominal obesity, one of the most critical types of obesity, is characterized by excessive visceral fat accumulation and increased inflammatory activity in adipose tissue, playing a decisive role in the onset and progression of metabolic disorders. Inflammatory markers such as interleukin-1 beta (IL-1β) and innate immune pathways associated with macrophages, including Dectin-1, directly contribute to chronic inflammation, insulin resistance, and glucose dysregulation. IL-1β is considered a key pro-inflammatory cytokine; its elevated levels in abdominal adipose tissue disrupt glucose homeostasis and activate molecular pathways related to insulin resistance. Additionally, Dectin-1, expressed on macrophages and dendritic cells, promotes the secretion of cytokines and reactive oxygen species, exacerbating inflammation and contributing to the progression of obesity and diabetes. Although the anti-inflammatory and insulin-sensitizing effects of exercise—particularly aerobic and resistance training—are well established, findings regarding the effects of combined training on innate immune pathways and inflammatory markers such as Dectin-1 remain limited and sometimes inconsistent. Given that medium-term training protocols can significantly improve metabolic function, yet evidence on their effects on Dectin-1 and IL-1β in individuals with abdominal obesity is insufficient, the present study aimed to investigate the effects of 12 weeks of combined resistance and aerobic training on Dectin-1, IL-1β, and glycemic indices in men with abdominal obesity.

2. Materials and Methods

This semi-experimental study employed a pretest–posttest design with a control group. A total of 24 men aged 40–50 years with abdominal obesity from Kashan were selected through convenience sampling and randomly assigned to either the experimental group (n=12) or the control group (n=12). Inclusion criteria required participants to be male, have abdominal obesity, be free of cardiovascular diseases or diabetes, not be taking anti-inflammatory or hormonal medications, and have no limitations on physical activity.

The experimental group engaged in combined training three times per week for 12 weeks. The training protocol included both resistance and aerobic exercises. The resistance component involved bench press, lat pulldown, rowing, leg press, and quadriceps and hamstring exercises, performed in three sets of 10–12 repetitions with progressively increasing intensity, ranging from 55% to 80% of one-repetition maximum. Rest intervals were 45–60 seconds between sets and 1–2 minutes between exercises. The aerobic component, which included running or brisk walking, began at 50% of maximal heart rate and increased by 5% every two weeks until reaching approximately 75%. Session duration increased from 10 minutes at the start to 22 minutes by the end of the protocol. Exercise intensity was monitored using a Polar heart-rate monitor to ensure adherence to the protocol.

Before and after the intervention, anthropometric indices, muscular strength, maximal oxygen consumption, and blood variables—including Dectin-1, IL-1β, glucose, insulin, and insulin resistance—were measured. Blood samples were collected after 10–12 hours of fasting, one day before the start of training and 24 hours after completing week 12. Statistical analysis included paired t-tests for within-group comparisons and analysis of covariance (ANCOVA) for between-group comparisons, with the significance level set at p<0.05.

3. Results

According to the ANCOVA results, Dectin-1 (p=0.001, F=68.45), IL-1β (p=0.001, F=27.18), glucose (p=0.001, F=0.65), insulin (p=0.001, F=215), and insulin resistance (p=0.001, F=153.28) showed significantly greater reductions in the experimental group compared to the control group. Additionally, paired t-test results indicated significant reductions in Dectin-1 (12.0% decrease, p=0.001), IL-1β (12.36% decrease, p=0.01), glucose (16.7% decrease, p=0.001), insulin (18.4% decrease, p=0.001), and insulin resistance (31.01% decrease, p=0.001) in response to the training protocol.

4. Conclusion

Based on the findings, the 12-week combined resistance and aerobic training program implemented in this study can effectively reduce inflammation and improve metabolic markers in men with abdominal obesity. The significant reductions in Dectin-1 and IL-1β suggest that this training may lower systemic inflammation by modulating innate immune pathways and decreasing pro-inflammatory macrophage activity. Additionally, improvements in glycemic indices indicate enhanced insulin sensitivity, which helps reduce the risk of developing type 2 diabetes. Given its low cost, safety, and ease of implementation, combined training can be recommended as a practical and efficient approach for clinical and health-promotion programs targeting individuals with abdominal obesity. Overall, this study highlights the importance of combined exercise in managing inflammation and metabolic dysfunction, providing a foundation for future research on the role of innate immune mechanisms in response to exercise interventions.

5. Acknowledgment & Funding

We express our gratitude to the Research Deputy and the Department of Physical Education at the University of Kashan for their support.

6. Ethical Consideration

This study is derived from an MSc thesis in Exercise Physiology and Wellness, approved by the Research Deputy of the University of Kashan and registered in the IRANDOC system with ID 23104514 dated 20/01/2025.

7. Authors' Contributions

We sincerely thank all participants for their cooperation throughout the study period.

8. Conflict of Interest

The authors declare no conflict of interest.