Metabolic syndrome is a term used to describe a complex clinical condition that includes abdominal obesity, increased level of serum triglycerides, elevated blood pressure, decreased level of high-density lipoprotein cholesterol, and high fasting glucose level. Metabolic syndrome represents one of the major risk factors for the development of cardiovascular diseases and type 2 diabetes mellitus. According to the results of numerous previously conducted studies, the prevalence of metabolic syndrome among the individuals with schizophrenia is higher than in the general population.

The reasons for the higher prevalence of metabolic syndrome among the individuals with schizophrenia are not yet fully clarified. Nevertheless, unhealthy dietary habits are considered to be one of the main factors that could have an impact on metabolic syndrome development. According to the results of published studies, individuals with schizophrenia have poorer dietary habits when compared to people without mental disorders.

Although there are numerous previously published studies focused on the impact of nutritional interventions on metabolic syndrome in individuals with schizophrenia, there is still no consensus on what would be the most appropriate nutrition therapy for the treatment of metabolic syndrome in this specific population group. Furthermore, the vast majority of the published studies have been conducted on outpatients, with only a small number of them being carried out on hospitalized individuals with a diagnosis of schizophrenia.

Dietary Approaches to Stop Hypertension (DASH) diet is primarily intended to those individuals with elevated blood pressure, but according to some authors, it could have beneficial effects in the treatment of the metabolic syndrome as well. DASH diet represents a healthy way of eating with a special emphasis on low-fat dairy products, fruits, vegetables and whole grains, together with an overall reduction in sodium intake.

Therefore, the present study aims to determine the impact of dietary habits and nutrition intervention on metabolic syndrome parameters in hospitalized individuals with the diagnosis of schizophrenia.

The investigators hypothesize that the intervention will result in the improvement in metabolic syndrome parameters, the amelioration in dietary habits, and the reduction in body weight.

Inclusion Criteria:

• the diagnosis of schizophrenia according to the 10th Revision of the International Classification of Diseases (ICD-10)
• age 18-67
• the diagnosis of metabolic syndrome according to the Joint Interim Statement definition
• taking antipsychotic medication for the last 6 months or more
• a stable phase of schizophrenia
• provided written informed consent (for participants deprived of legal capacity, provided written informed consent of both the participants and their legal guardians)

Exclusion Criteria:

• older than 67
• without the diagnosis of schizophrenia and/or metabolic syndrome
• following one of the specific hospital diets with the restrictions related to the intake of specific food items, groups or nutrients
• taking medications for the reduction of body weight
• significant body weight loss in the past 3 months
• refusing to provide written informed consent
• on personal request
• deterioration in participant's mental state
• the occurrence of a new illness that could unable full participation in the study or could have an interfering effect
• a significant change in pharmacological therapy during the intervention period
• cognitive impairments that unable full participation in the study
• lack of interest or refusal to fully participate in the study
• hospital discharge during the intervention period