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This observational study aims to evaluate the diagnostic and prognostic value of the systemic immune-inflammatory index (SII) and the systemic inflammation response index (SIRI) in individuals with overweight or obesity. The study will assess their association with obesity status, metabolic complications, lifestyle patterns, dietary indices, and established inflammatory biomarkers. Participants will undergo anthropometric assessment, laboratory testing, dietary evaluation, and follow-up for response to different obesity treatment modalities over 3 years. The study intends to determine whether SII and SIRI can serve as clinically useful predictors of metabolic risk and treatment outcomes of obesity.
Obesity is a complex chronic disease associated with systemic low-grade inflammation, metabolic dysfunction, and increased risk of comorbidities such as type 2 diabetes, dyslipidemia, nonalcoholic fatty liver disease, and cardiovascular disease. Adipose tissue acts as an active endocrine organ, influencing immune regulation and inflammatory signalling. Although numerous inflammatory biomarkers have been evaluated in obesity, the diagnostic performance of novel composite systemic immune-inflammatory indices, particularly the systemic immune-inflammation index (SII) and the systemic inflammation response index (SIRI), remains inadequately characterised. SII and SIRI, derived from peripheral blood counts, have shown prognostic potential in various clinical settings but have not been systematically evaluated in predicting metabolic complications or treatment response in obesity. This study seeks to expand their application in patients with overweight and obesity by 1) evaluating the cross-sectional associations between SII/SIRI and obesity severity, inflammatory biomarkers, metabolic disorders, and dietary patterns; and 2) determining the prognostic value of SII/SIRI for predicting metabolic complications and clinical response to behavopural and lifestyle modification, pharmacotherapy, and bariatric surgery over a 1-year follow-up.
Participants will complete anthropometric measurements, comprehensive biochemical profiling, inflammatory cytokine assessment, dietary evaluation, and structured follow-up at 12 and 24 weeks, with continued monitoring of treatment response and metabolic outcomes over 1 year.
STUDY PROCEDURES (Structured per visit) Visit 1 - Baseline (Week 1)
Visit 2 - Week 12
Visit 3 - Week 24
LONG-TERM FOLLOW-UP (Year 1)
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Overweight and obesity cohort | Adults with overweight or obesity presenting to outpatient obesity clinics. Participants aged ≥18 years with BMI ≥25 kg/m² undergoing clinical evaluation for obesity. All participants will follow the same assessment and follow-up schedule; variation occurs only in the type of treatment chosen (lifestyle, pharmacotherapy, bariatric surgery). |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Nutritional counselling | Behavioral | Participants will receive interventions that are part of routine medical care, i.e. structured personalised nutritional intervention aligned with the Croatian Guidelines for the Treatment of Adults with Obesity. It emphasises lifestyle modification, energy-reduced dietary patterns, and the adoption of healthy eating habits as the first-line approach to weight management. The intervention consists of a 30-minute individualised counselling session delivered by a licensed nutrition professional. During the session, participants are guided to adopt a Mediterranean diet, with goal-setting, portion guidance, and strategies to increase adherence. The routine medical intervention aligned with the guidelines' recommendation for a nutritionally balanced diet combined with a modest daily energy deficit (~500 kcal) to support gradual, sustainable weight loss and long-term weight maintenance. |
| Measure | Description | Time Frame |
|---|---|---|
| Diagnostic and prognostic value of SII and SIRI | The diagnostic and prognostic value of systemic inflammation indices (SII and SIRI) will be assessed using ROC curve analysis, including sensitivity, specificity, and AUC calculations. | baseline, 24 weeks and at study completion, an average of 1 year |
| Measure | Description | Time Frame |
|---|---|---|
| Association of SII and SIRI with Metabolic Complications | The association of SII and SIRI with metabolic complications (insulin resistance, dyslipidemia, NAFLD) and their ability to predict response to obesity treatment (behavioural and pharmacologic) will be evaluated. | baseline, 24 weeks and at study completion, an average of 1 year |
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Inclusion Criteria
Exclusion Criteria
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The study population consists of adults with overweight or obesity who are receiving obesity management at outpatient obesity clinics. Eligible participants are 18 years or older and have a BMI between 25.0-29.9 kg/m² (overweight) or BMI ≥ 30 kg/m² (obesity). All participants must be able to attend scheduled clinical visits and must provide written informed consent.
| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Gordana Kenđel Jovanović, Asst.Prof. | Contact | +385912030704 | gordanakj@uniri.hr | |
| Jelena Vresk Špiranec, MD, spec. endocrinology | Contact | +385995112141 | jelenavresk@gmail.com |
| Name | Affiliation | Role |
|---|---|---|
| Gordana Kenđel Jovanović, Asst. Prof. | Faculty of Medicine, University of Rijeka | Principal Investigator |
| Sanja Klobučar, Assoc.Prof. | Faculty of Medicine, University of Rijeka; Clinical Hospital Rijeka | Study Director |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| General Hospital Varaždin | Recruiting | Varaždin | Croatia |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 40381089 | Background | Galasso M, Verde L, Barrea L, Savastano S, Colao A, Fruhbeck G, Muscogiuri G. The Impact of Different Nutritional Approaches on Body Composition in People Living with Obesity. Curr Obes Rep. 2025 May 17;14(1):45. doi: 10.1007/s13679-025-00636-w. | |
| 40920291 | Background | Barrea L, Verde L, Annunziata G, Chedraui P, Petraglia F, Cucalon G, Camajani E, Caprio M, Gorini S, Iorio GG, Di Girolamo R, Carbone L, Chapela S, Frias-Toral E, Muscogiuri G. Effectiveness of Medical Nutrition Therapy in the Management of Patients with Obesity and Endometriosis: from the Mediterranean Diet To the Ketogenic Diet, Through Supplementation. The Role of the Nutritionist in Clinical Management. Curr Obes Rep. 2025 Sep 8;14(1):68. doi: 10.1007/s13679-025-00662-8. |
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Participants' demographics, obesity management treatments, and outcomes.
The IPD will be available after the completion of the study, starting on 1st January of 2028, to January of 2033.
Access will be provided to qualified researchers engaged in independent scientific research. Anonymised or pseudonymized participant-level data will be shared to protect privacy. Data will be provided via a secure, managed-access data sharing repository.
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| ID | Term |
|---|---|
| D050177 | Overweight |
| D009765 | Obesity |
| D007249 | Inflammation |
| D024821 | Metabolic Syndrome |
| ID | Term |
|---|---|
| D044343 | Overnutrition |
| D009748 | Nutrition Disorders |
| D009750 | Nutritional and Metabolic Diseases |
| D001835 | Body Weight |
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Frozen serum/plasma aliquots for analysis of inflammatory biomarkers (hs-CRP, IL-6, TNF-α, adiponectin).
|
| Association of SII and SIRI with Dietary Patterns |
The relationship between SII/SIRI and adherence to anti-inflammatory and pro-inflammatory dietary patterns will be examined using indices such as the Mediterranean Diet Index and the Dietary Inflammatory Index. The analysis will provide insight into the impact of diet quality on systemic inflammation over time. |
| baseline, 24 weeks and at study completion, an average of 1 year |
| Identification of Prognostic Markers of Metabolic Comorbidities | Inflammatory indices (SII, SIRI) and monitored biomarkers will be analysed to determine their ability to predict the development or progression of obesity-related metabolic complications. The aim is to identify early indicators of increased risk for adverse metabolic outcomes and help in providing timely and appropriate obesity management. | baseline, 12 weeks, 24 weeks, and at study completion, an average of 1 year |
| Changes in SII and SIRI During Treatment | Longitudinal changes in SII and SIRI will be monitored throughout the treatment period to assess the degree and sustainability of systemic inflammation reduction. Results will be associated with clinical outcomes and treatment effectiveness. | baseline, 12 weeks, 24 weeks, and at study completion, an average of 1 year |
| Relationship Between SII/SIRI and Inflammatory Biomarkers | The associations between SII and SIRI and inflammatory biomarkers will be examined to confirm their biological significance and diagnostic value. This analysis will contribute to understanding the mechanisms of systemic inflammation in the context of obesity and metabolic disorders. | baseline, 12 weeks, 24 weeks, and at study completion, an average of 1 year |
| 41377417 | Background | Mirchandani M, Jeanty H, Sahu S, Nejati H, Adla Jala SR, Mahapatro A, Jain SM, Nasrollahizadeh A, Arezoo G, Hashemi SM, Amini-Salehi E. Exploring the Systemic Immune-Inflammation Index as a novel biomarker for nonalcoholic fatty liver disease: a systematic review and meta-analysis. Ann Med Surg (Lond). 2025 Oct 15;87(12):8748-8756. doi: 10.1097/MS9.0000000000004097. eCollection 2025 Dec. |
| 40247599 | Background | Asemani S, Jourabchi-Ghadim N, Arefhosseini S, Ebrahimi-Mameghani M. Weight-adjusted waist index and its relationship with systemic inflammatory Index and metabolic indices in overweight and obese individuals: A cross-sectional study. Sci Prog. 2025 Apr-Jun;108(2):368504251333218. doi: 10.1177/00368504251333218. Epub 2025 Apr 17. |
| 39885869 | Background | Liao Y, Zhou K, Lin B, Deng S, Weng B, Pan L. Associations between systemic immune-inflammatory index and visceral adipose tissue area: results of a national survey. Front Nutr. 2025 Jan 16;11:1517186. doi: 10.3389/fnut.2024.1517186. eCollection 2024. |
| 39127686 | Background | Zhou Y, Wang Y, Wu T, Zhang A, Li Y. Association between obesity and systemic immune inflammation index, systemic inflammation response index among US adults: a population-based analysis. Lipids Health Dis. 2024 Aug 10;23(1):245. doi: 10.1186/s12944-024-02240-8. |
| 39294646 | Background | Liu X, Zhang Y, Li Y, Sang Y, Chai Y, Zhang L, Zhang H. Systemic immunity-inflammation index is associated with body fat distribution among U.S. adults: evidence from national health and nutrition examination survey 2011-2018. BMC Endocr Disord. 2024 Sep 18;24(1):189. doi: 10.1186/s12902-024-01725-y. |
| 39069464 | Background | Qiu L, Ren Y, Li J, Li M, Li W, Qin L, Ning C, Zhang J, Gao F. Association of systemic immune inflammatory index with obesity and abdominal obesity: A cross-sectional study from NHANES. Nutr Metab Cardiovasc Dis. 2024 Oct;34(10):2409-2419. doi: 10.1016/j.numecd.2024.06.003. Epub 2024 Jun 13. |
| 39987171 | Background | Zhang YZ, Ma RW, Bhandari S, Xie J, Zhang XY, Xie C, Duan H, Meng J, Wu QY, Liu K, Feng B, Cheng LM. Association between systemic immune inflammation index and adolescent obesity in a cross-sectional analysis. Sci Rep. 2025 Feb 22;15(1):6439. doi: 10.1038/s41598-025-91125-6. |
| 41374089 | Background | Uzun H, Fenercioglu AK, Senyigit A, Can G. Relationship Between Nutritional Status and Systemic Immune-Inflammation Indices Across BMI Categories. Nutrients. 2025 Dec 3;17(23):3799. doi: 10.3390/nu17233799. |
| D012816 |
| Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
| D010335 | Pathologic Processes |
| D007333 | Insulin Resistance |
| D006946 | Hyperinsulinism |
| D044882 | Glucose Metabolism Disorders |
| D008659 | Metabolic Diseases |