The overall objective of this study is to evaluate the effectiveness of an optimized lifestyle intervention based on dietary advice, behavioral support, and provision of key foods compared to dietary advice with behavioral support or dietary advice alone. The intervention aims to improve nutritional status, metabolic risk factors, and planetary sustainability.

A total of 300 participants (150 men and 150 women) who meet all inclusion criteria and none of the exclusion criteria will be recruited. The study will be conducted at the Centre for Lifestyle Intervention at Östra Hospital in Gothenburg, led by researchers from Chalmers University of Technology, University of Gothenburg, and Sahlgrenska University Hospital. Participants will be recruited from two different socioeconomic areas in Gothenburg to examine how dietary interventions function in diverse population groups.

The study follows a twelve-week randomized, controlled, parallel intervention design. Participants will be randomized into three groups, each with 100 individuals:

Optimized lifestyle intervention group - receiving dietary advice, behavioral support, and provision of key foods.

Behavioral support intervention group - receiving dietary advice and behavioral support.

Control group - receiving dietary advice according to the SWITCH diet. The SWITCH diet, developed within the EU project SWITCH, is designed to align with European dietary guidelines and promote sustainable and healthy eating habits. It emphasizes whole grains, vegetables, fruits, legumes, and sustainable seafood while limiting processed foods, added sugars, and salt.

Throughout the study, participants will undergo clinical assessments at baseline, midpoint (week 7), and endpoint (week 13). Key measurements include anthropometric data, blood pressure, blood glucose, blood lipids, and inflammatory markers. Dietary intake and sustainability aspects of food consumption will also be evaluated. Participants in the intervention groups will receive personalized coaching and access to practical resources, such as meal plans, recipes, and visual educational materials.

The primary outcome of the study is the difference in cardiometabolic risk factors (e.g., blood lipids, blood pressure, glucose, insulin resistance markers) between the intervention groups. Secondary outcomes include changes in dietary intake, nutritional status markers, inflammatory markers, and sustainability measures (e.g., CO₂ emissions, land use, biodiversity impact). Additionally, exploratory analyses will investigate associations between diet, lifestyle changes, gut microbiota, and metabolic responses.

This study aims to generate valuable insights into the effectiveness of different dietary intervention strategies in real-life Nordic conditions. The results will contribute to the development of evidence-based recommendations for sustainable and health-promoting dietary patterns.

Inclusion Criteria:

• Age 18-70 years
• Body mass index 25-35 kg/m2
• Stable dietary patterns at the entry to the study (no specific dieting the last 4 weeks).
• Willingness to adhere to advised diet pattern and to consume provided key foods.
• Medications stable for the previous 14 days of relevant medicines
• Access to a -18⁰ C freezer to store key foods at home.
• Signed informed consent

Exclusion Criteria:

• Currently having an infection or other relevant illness.
• Cardiovascular events (myocardial infarction or stroke) during the previous 6 months. To be included, the disease needs to be stable.
• Diagnosis of diabetes (any type).
• Blood Pressure (BP): ≥185/105 mmHg.
• Serum Cholesterol (S-Chol): ≥8 mmol/L.
• Blood Glucose (B-Glucose): fasting value >7 mmol/L.
• Currently on GLP-1 receptor agonists.
• History of stomach or gastrointestinal diagnoses (inflammatory bowel disease, Crohn's disease, hepatitis, malabsorption, celiac disease etc.).
• IBS- if severe and recent (<0.5year)?
• Previous colostomy, bowel resection, bariatric surgery or other major gastrointestinal surgery.
• Renal or liver failure (creatinine <1.7 mg/dl and alanine aminotransferase/ aspartate aminotransferase > 2 times than normal values (ASAT, ALAT), respectively).
• Anemia or Hemoglobin (Hb): <100 g/L
• Blood donation (or participation in a clinical study with blood sampling) within 30 days prior to inclusion
• Currently on a specific diet.
• A diet incompatible with protocol diets such as strict vegan/vegetarian.
• Food allergies or intolerances to food items included in the intervention.
• High level of regular physical activity at baseline - scale 4 on SG-PALS.
• History of drug or alcohol abuse.
• Not able to understand written or spoken Swedish.
• Any other reason for lack of suitability for participation in the trial, as judged by the principal investor and/ or the clinical investigator.
• Pregnant or lactating or planning to become pregnant during the study period.
• Involved in another potentially interfering research study.