The present study investigates the effect of Mediterranean Diet and Mindful Eating on depression severity in people with obesity and major depressive disorder. The factorial design allows to investigate potential synergistic effects of the interventions. Participants will be randomized to one of the four intervention groups (mediterranean diet, mindful eating, their combination and a befriending control group). The intervention consists of a 12-week period, followed by a 12-week follow up. The primary outcome is depression severity.

Depression and obesity are highly prevalent diseases that are strongly correlated. There is a growing gap in care and treatment options for those affected. The effectiveness of a Mediterranean Diet on mental health has already been shown in various studies. Additionally to physiological effects of nutrient intake, also the psychological factor of changing the way of eating seem to play a role. The present study investigates the effect of a Mediterranean Diet and Mindful Eating on depression severity in people with obesity and clinically diagnosed major depressive disorder. The factorial design allows to investigate potential synergistic effects of the interventions. Participants will be randomized to one of the four intervention groups (mediterranean diet, mindful eating, their combination and a befriending control group). The intervention consists of a 12-week period, where five individual nutrition consueling meetings will take place, followed by a 12-week follow up. The primary outcome is depression severity. Secondary outcomes and analyzes include quality of life, self-efficacy, mediterranean diet and mindfulness eating scores, anthropometric measurements, as well as mediator and moderator analysis, a microbiome analysis, a qualitative evaluation and an economic analysis.

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

data analysis will be conducted blinded