• Patients with schizophrenia spectrum disorders (International classification of diseases; ICD-10: DF2x) or bipolar disorder (ICD-10: DF30.x or DF31.x)

• Medical treatment with antipsychotics

• Age 18-45 years

• Legally competent

• Able to give informed consent

⁃ and either:

⁃ \- Body mass index (BMI) ≥30 kg/m2.

⁃ Or

• BMI ≥27 kg/m2 and at least one of the following:

• Hypertension defined as treatment with ≥1 antihypertensive drug or out-of-office / 24-hour, non-invasive ambulatory blood pressure ≥140/90 mmHg within the previous 6 months

• Dyslipidaemia defined as treatment with ≥1 lipid-lowering drug or elevated low-density lipoprotein (LDL) cholesterol (≥3.0 mmol/l), elevated triglycerides (≥1.7 mmol/l) or low high-density lipoprotein cholesterol (≥1.2 mmol/l in women and ≥1.0 mmol/l in men) within the previous 6 months

• Sleep apnoea (ICD-10 DG473).

• Prediabetes or diabetes defined as HbA1c ≥42 mmol/mol or impaired fasting glucose as defined by the International Diabetes Federation within the previous 6 months.

⁃ Or

⁃ \- a history of rapid weight gain during antipsychotic therapy defined as increases of either ≥5% body weight or ≥5 cm waist circumference since initiation of antipsychotic therapy.