The Effect of Mediterranean Diet and Mindfulness Eating on Depression Severity in People With Obesity and Major Depressive Disorder

Inclusion Criteria: * Age ≥ 18 years * Presence of clinically diagnosed major depression * At least moderate depression severity: BDI-II ≥ 20 * obesity: BMI ≥ 30 kg/m2 * Stable co-intervention: no change in the type, dosage or frequency of antidepressant medication and/or psychotherapy four weeks before and during the study * Low adherence to the mediterranean diet: MEDAS \< 10 * Low adherence to mindful eating: MEI \< 5.13 Exclusion Criteria: * Diseases of the gastrointestinal tract that do not allow adequate implementation of the intervention (e.g. irritable bowel syndrome, post-bariatric surgery, colorectal carcinoma) * Metabolic diseases with strong impact on intervention (e.g. type 1 diabetes mellitus, chronic kidney disease) * Severe food allergies and intolerances, that do not allow adequate implementation of the intervention * Diagnosed, current psychological comorbidities (bipolar disorder, eating disorder, personality disorder, psychosis) * intake of antibiotics in the last three months current substance abuse * Pregnancy and breatfeeding * Suicidal ideation * unable to participate or complete questionnaires Healthy Volunteers: samples of 32 healthy volunteers are included for microbiome analysis only ( inclusion criteria: * age ≥ 18 years * BMI 20 - 30 kg/m\^2 exclusion criteria: * depression or other psychological comorbidities (bipolar disorder, eating disorder, personality disorder, psychosis) * high adhernece to mediterranean diet: MEDAS ≥ 10 * high adherence to mindful eating: MEI ≥ 5.13 * Diseases of the gastrointestinal tract or metabilic diseases (e.g. irritable bowel syndrome, post-bariatric surgery, colorectal carcinoma, type 1 diabetes mellitus) \-- intake of antibiotics in the last three months current substance abuse * pregnancy or breastfeeding