Mediterranean Diet- and Psychological Well-being Theory-based Intervention to Reverse Metabolic Syndrome in Chile

Promotion of MedDiet adherence and psychological well-being in Chile offers a great potential to confront our ongoing epidemiological transition to increased risk factors and non-communicable chronic diseases. The main aims of this clinical trial are to design, implement, and evaluate the impact of a MedDiet- and psychological well-being-based intervention on reversal rate of MetS -compared to a control low fat diet- in Chilean adult population.

BACKGROUND: Non-communicable diseases (NCDs) are currently major causes of morbidity and mortality as well as economic healthcare burden worldwide, including Chile. Predisposing psychosocial as well as lifestyle risk factors -such as an unhealthy diet- have driven this global increase in NCDs. Overall, the ongoing epidemiological transition and current health situation in our country calls out for an urgent need to further evaluation of disease-related psychosocial factors and diet as well as definition of evidence-based feasible and effective nutritional interventions in the Chilean population. In addition, dietary interventions may be more easily incorporated and followed if provided and supported by theory-based and contextually grounded psychological approaches within a comprehensive positive psychosocial framework.

Currently, the Mediterranean diet (MedDiet) is one of the healthiest dietary patterns based on observational studies in developed countries showing that adherence to this food intake pattern associates with lower prevalence/incidence of several NCDs, including metabolic syndrome (MetS), and reduced total mortality. Far fewer interventional studies -essentially performed in Europe and some of them questioned due to methodological issues and others with inconsistent findings- have reported favorable effects of MedDiets on clinical outcomes. Thus, impact of MedDiet on high-risk conditions (i.e., MetS) and clinical end-points in populations outside the Mediterranean Basin remains unknown. Thus, additional interventional studies about this dietary pattern on disease outcomes in more diverse populations, including our country, are needed.

A Mediterranean lifestyle goes beyond mere food intake: it includes promotion of psychosocial resources, community life as well as cultural traditions. Indeed, Mediterranean lifestyle is a real way of life that integrally promotes physical, mental, and social well-being. However, psychological well-being (PWB) is much more than absence mental disorders. From a positive framework, PWB encompasses emotional/subjective well-being together with effective psychological functioning within a favorable social context and has been associated with healthy behaviors, positive health outcomes, and longevity. Promotion of PWB is in fact an emerging goal in healthcare, shifting the focus from treating/preventing mental disease to enhancing positive aspects of mental health. If PWB interventions are feasible and effective in boosting adherence to health behaviors, they may become a cost-effective tool to improve biomarker, functional and clinical outcomes related to NCDs.

Based in this latter broad and positive psychosocial paradigm, promotion of PWB may facilitate acquisition and routine practice of healthy lifestyles, such as MedDiet, decreasing risk of NCDs. However, to our knowledge, PWB theory-based interventions have not been tested as a new approach to increase MedDiet adherence. Based on the multi-construct model of this theory, which is consistent with a Mediterranean lifestyle, a comprehensive PWB intervention program may increase adherence to MedDiet and -in turn- enhance its impact on chronic disease risk conditions such as MetS.

Remarkably, Central Chile has a Mediterranean-like environment and food production comparable to those present in Mediterranean countries. Chilean culinary traditions also use ingredients and cooking techniques similar to Mediterranean cuisine. Thus, promotion of MedDiet adherence in Chile offers a great potential to confront our ongoing epidemiological transition to increased risk factors and NCDs. Despite our geography, food production, culinary traditions, and potential health benefits, very few studies have evaluated the potential impact of MedDiet patterns on health and/or disease in Chilean subjects. Furthermore, these studies exhibit important methodological limitations, such as only cross sectional observational analysis or small sample sizes, no control comparators for interventions, lack of theory-based behavior change advice, and use of intermediate biomarkers rather than clinical end-points. Better designed intervention studies using a locally tailored MedDiet index, feasible dietary prescription, novel PWB advice strategies as well as comprehensive outcome evaluation are required to further support and more extensively implement this dietary pattern and its associated positive psychosocial features for NCD prevention and treatment in our population.

GUIDING HYPOTHESES. A psychological well-being theory-based behavioral support increases long-term MedDiet adherence and this nutritional intervention combined with promotion of psychological well-being is more effective at reversing MetS in Chilean subjects (primary outcome) and improving additional relevant biomarkers, clinical conditions, and well-being (secondary outcomes) compared to individuals following a low fat dietary pattern alone.

OVERALL AIMS: 1. To design a PWB intervention as well as to refine a MedDiet pattern adapted and contextualized to Chilean subjects; 2. To determine if a customized psychological well-being intervention facilitates initiation and long-term adherence to a MedDiet dietary pattern in Chilean subjects with MetS; 3. To demonstrate that a locally adapted MedDiet pattern in association with a psychological well-being intervention -versus a low fat diet alone- increases the reversal rate of MetS; and 4. To establish whether this dietary approach with or without a psychological intervention improves traditional and novel disease biomarkers as well as non-alcoholic fatty liver disease and psychological well-being -compared to a control low fat diet- in Chilean subjects with MetS.

METHODOLOGY. Overall, this proposal will design and implement a PWB theory-based behavior change strategy to increase MedDiet adherence and perform a clinical MedDiet intervention as main experimental research approaches. A tailored contextualized PWB intervention will be designed using information derived from focus group-based qualitative research. Then, a parallel-group randomized controlled clinical trial will be developed to determine the impact of MedDiet- and psychological well-being theory-based nutritional intervention on MetS (primary end-point), disease-associated biomarkers, fatty liver disease, depression, quality of life, and psychological well-being (secondary outcomes). Appropriate study protocols, anthropometric, questionnaire-based, biochemical, imaging, and clinical follow-up evaluations as well as proper statistical approaches will be implemented and applied in the RCT study.

SIGNIFICANCE AND IMPLICATIONS: If the main findings turn out as expected (psychological well-being intervention facilitates adherence to MedDiet and this combined intervention reduces MetS and improves related-secondary clinical and psychosocial outcomes), this research proposal will provide further evidence on the beneficial health effects of the MedDiet beyond the Mediterranean basin, particularly in our country. Based on this locally generated evidence, MedDiet associated with promotion of positive psychosocial resources may be more compellingly applied to promote physical health and well-being as well as to prevent and treat NCD at individual and population levels in Chile.

Eligibility Criteria:
Inclusion Criteria:

Adult men or women 25-70 years-old with existing metabolic syndrome defined as the presence of at least three of the following criteria: (i) abdominal obesity (waist circumference \>90 cm in men or \>80 cm in women), (ii) low HDL-cholesterol (\<40 mg/dl in men or \<50 mg/dl in women) or under HDL increasing drugs, (iii) high triglycerides (TG) (≥ 150 mg/dl) or under TG lowering drugs, (iv) high blood hypertension (blood pressure ≥ 130/85 mmHg) or under treatment, and (v) high blood glucose (fasting plasma glucose concentration ≥ 100 mg/dl) or under treatment.

Exclusion Criteria:

* Absence of written informed consent
* Inability/low chance of adherence to diets or attend scheduled visits
* Allergy or intolerance to foods included in either interventional diets
* Recent (\<12 months) participation in weight loss program
* Obesity with BMI \>35 kg/m2 or due to endocrine diseases, with exception of treated hypothyroidism
* Type 1 diabetes, unstable type 2 diabetes
* Uncontrolled high blood pressure
* Previous clinical atherosclerotic cardiovascular disease
* Use of medications such as weight loss drugs, oral corticoids, immunosuppressants or cytotoxic agents
* Advanced chronic liver disease
* Previous organ transplantation
* History of HIV-positive status or AIDS
* History of inflammatory bowel disease or major gastrointestinal surgery (bariatric surgery, bowel resection)
* Active psychiatric conditions: eating disorders, severe depression, bipolar disorder, schizophrenia
* Short (\<2 years) life expectancy
* Current or previous (within the last year) participation in other clinical trials with dietary or drug interventions
* Institutionalized subjects
* Additional conditions that may limit adherence to the study