Patients with schizophrenia receiving long-term antipsychotic therapy are at increased risk of chronic low-grade inflammation and metabolic disturbances, which contribute to poor physical health outcomes and increased cardiovascular morbidity. Structured Medical Nutrition Therapy (MNT), consisting of individualized nutrition assessment, dietary intervention, nutrition education, and regular monitoring, has the potential to improve dietary quality and modulate systemic inflammation. This study aims to evaluate the effect of Structured Medical Nutrition Therapy on the Systemic Inflammation Index (SII), a novel inflammatory biomarker derived from neutrophil, lymphocyte, and platelet counts, in patients with schizophrenia receiving antipsychotic therapy. It is hypothesized that patients receiving structured MNT will demonstrate a greater reduction in SII compared with those receiving standard nutritional care, supporting the integration of evidence-based nutritional interventions into the comprehensive management of schizophrenia to improve metabolic and inflammatory outcomes.

Inclusion Criteria:

Adults aged 18-60 years. Diagnosed with schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).

Receiving stable antipsychotic therapy for at least 4 weeks before enrollment. Hospitalized at Prof. Dr. M. Ildrem Psychiatric Hospital during the study period.

Able to consume an oral diet. Willing to participate and provide written informed consent (or consent provided by a legally authorized representative when applicable).

Exclusion Criteria:

Acute infection, autoimmune disease, malignancy, or other inflammatory conditions that may influence the Systemic Inflammation Index (SII).

Chronic liver disease, end-stage renal disease, or severe heart failure. Pregnancy or breastfeeding. Current use of systemic corticosteroids, immunosuppressive agents, or anti-inflammatory medications that could affect inflammatory biomarkers.

Receiving enteral or parenteral nutrition. Participation in another interventional clinical trial within the previous 3 months.

Incomplete clinical or laboratory data. Inability to complete the intervention or follow-up assessments.