Intensive Weight Loss Intervention Versus Usual Care for Adults With Obesity

Please note that participants need to be invited in order to take part in the trial. Inclusion Criteria: 1. Age ≥18 years and ≤60 years old at screening. 2. BMI ≥30 kg/m2 or ≥27.5 kg/m2 in people with South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family backgrounds (as reported by the participants). 3. Informed consent. Exclusion Criteria: 1. Has severe and complex obesity, i.e., obesity class II (BMI≥35 if white or 32.5 if non-white) with one or more of these specific adiposity-related comorbidities: cardiovascular disease, type 2 diabetes, hypertension, non-alcoholic steatosis, or sleep apnoea (Appendix 1). 2. Intending to become pregnant in the next two years, or pregnant, or breastfeeding. 3. Use of WLM or GLP-1 agonist treatment within the last 3 months. 4. Currently being treated for cancer other than oestrogen antagonist therapy or non-melanoma skin cancer. 5. Prior bariatric surgery, not including laparoscopic gastric banding, intragastric balloons or duodenal-jejunal bypass sleeve (Endobarrier™ or similar) if the device has been removed \>1 year before screening. 6. Diagnosis or treatment for eating disorder within the last 6 months. 7. Any other disease that markedly compromises the participant's ability to adhere to the treatment programme or follow-up or is likely to mean that weight loss will not improve the person's length or quality of life, such as conditions limiting life expectancy. 8. Conditions that contraindicate or complicate total diet replacement (including type 1 diabetes or other diabetes requiring any insulin therapy, phenylketonuria, or other conditions requiring special diets). 9. Taking part in other research involving multidisciplinary obesity treatment that would compromise participation in this trial. 10. Conditions that contraindicate or complicate GLP-1 or GIP agonist treatment (including history of pancreatitis) 11. Another member of the household enrolled in the trial.