1. Informed oral and written consent

2. Diagnosed with a mental illness according to the criteria of ICD10

3. Hospitalised at a forensic psychiatric department during the full inclusion period

4. Age 18 years to 65 years (both included)

5. BMI ≥27 kg/m2 with one or more weight-related comorbidities (sleep apnea, hypertension (BT ≥ 140/90 mmHg with no antihypertensive treatment. BT ≥ 130/80 mmHg with antihypertensive treatment), dyslipidaemia (LDL cholesterol ≥ 3 mmol/L), pre-diabetes (HbA1c 39-47 mmol/mol) or type 2 diabetes (HbA1c ≥ 48 mmol/mol)) or BMI ≥30 kg/m2

1. Any use of coercive measures according to the Danish law for Mental Health/Psykiatriloven (as defined in "Informationsbekendtgørelsen § 10").

2. Fertile females of child-bearing potential who are pregnant, breast-feeding or have the intention of becoming pregnant

3. Women who are not willing to use an adequate contraceptive considered as highly effective (IUD or hormonal contraception during the full length of the study

4. Impaired hepatic function (plasma liver transaminases >2 times the upper normal limit)

5. Impaired renal function (serum creatinine >150 μmol/l and/or macroalbuminuria)

6. Impaired pancreatic function (acute or chronic pancreatitis and/or plasma amylase >2 times the upper normal limit)

7. Cardiac problems defined as decompensated heart failure (NYHA class III/IV), unstable angina pectoris and/or myocardial infarction within the last 12 months

8. Hypertension with systolic blood pressure >180 mmHg or diastolic blood pressure >100 mmHg

9. Any condition that the investigator feels would interfere with trial participation

10. Use of weight-lowering pharmacotherapy within the preceding 3 months

11. Type 1 diabetes

12. Patients treated with insulin

13. Patients treated with other GLP-1 receptor agonist medicines

14. Known allergy to liraglutide or any of the ingredients in Saxenda®