BMI \> 50kg·m-2

Current pregnancy or breastfeeding, or intention to fall pregnant within the next 3 months

Uncontrolled hypertension (blood pressure \>200/120mmHg)

Current treatment with insulin

Current or recent use of GLP-1 agonists

Previous adverse reaction to a GLP-1 agonist

Current or recent involvement in a VLCD programme (within the last 12 months)

History of \>5% weight loss within the preceding 12 months

Ingestion of exogenous D2O within the preceding 12 months

Background of clinically significant cardiovascular, cerebrovascular or respiratory disease, neurological disorders or musculoskeletal problems

History of malignancy undergoing current treatment or palliation

History of any medical condition contraindicating the use of GLP-1 agonist medication

Any other medical condition deemed by the investigators to preclude inclusion into the study

Glucagon-like Peptide-1 Agonism With Very Low Calorie Diets