Low EnerGy DiEt iN Adolescents With Obesity and Type 2 Diabetes: The LEGEND Study

Inclusion criteria LED intervention * Diagnosis of T2DM (defined as an HbA1C ≥48mmol/mol, in the absence of features of type 1 or monogenic/syndromic diabetes). * Current HbA1C ≥48 (or ≥42 on antidiabetic medication) and ≤ 80 mmol/mol. To allow for the day-to-day variation in HbA1C and differences between point of care laboratory tests, -2 or +2 mmol/mol in the HbA1C result will be allowed in the current criteria if one of them is between or equal to 42-80mmol/mol. * Aged 12 to 17 years old. * BMI ≥981st centile (+2 SD) for age and sex (UK90 growth reference data). * Informed consent: * Received from the young person (age 16-17) OR * Received from young person's parent/carer, with patient assent (age 12-15). * Willing to engage in and commit to low energy diet, FR and weight management phases including follow-up and attending study visits. LED Intervention Interviews The same interview inclusion criteria for LED intervention, with the following additional requirements: Patients: * Informed consent: * Received from the young person (age 16-17) OR * Received from young person's parent/carer, with patient assent (age 12-15). * Willing to take part in a qualitative interview alongside a parent/carer. Relative/Carer: * A relative/carer for a young person meeting the above LED participant eligibility criteria. * Informed consent from the relative/carer to participate in the interview. * Willing to take part in a qualitative interview alongside the young person. Non-LED Qualitative Interview only participants * Diagnosis of T2DM (defined as an HbA1C ≥48mmol/mol, in the absence of features of type 1 or monogenic/syndromic diabetes). * Current HbA1C ≥48 (or ≥42 on antidiabetic medication) and ≤80 mmol/mol. * Aged 12 to 17 years old. * BMI ≥91st centile (+2 SD) for age and sex (UK90 growth reference data). * Informed consent: * Received from the young person (age 16-17) OR * Received from young person's parent/carer, with patient assent (age 12-15). * Willing to take part in a qualitative interview alongside a parent/carer only. HCPs * Registered HCP. * Experience of delivering this trial to the adolescents. * Willing to take part in a qualitative interview about undertaking motivational interviewing training and conducting/delivering the LED intervention study. Exclusion criteria LED intervention * HbA1C greater than 82mmol/mol (to allow for the variation in HbA1c differences). * Presence of diabetes-related autoantibodies, as per local centre guidelines. * Confirmed mono-genetic cause of obesity (e.g. SIM1 mutation) or diabetes-associated syndrome such as Prader-Willi syndrome, Bardet-Biedl or Wolfram's syndrome. * Secondary diabetes (post bone marrow transplant/chemotherapy). * Significant psychiatric co-morbidity. * Breastfeeding, pregnant or planning to conceive during the LED and FR phases (female participants will be advised on need for effective contraceptive methods during the 12-month study period, section 5.1.1.10). * Any other condition which, in the opinion of the study investigator, would make it inappropriate to undertake a period of LED. (All reasons for not approaching patients will be recorded and analysed anonymously. Cases can be discussed with the core study group if there is doubt). * Participation in another interventional trial within 6 months. * Informed consent and/or assent not received. * Pre-existing retinopathy. * Dietary avoidance (including, but not limited to, due to allergies, intolerances, religious reasons and lifestyle choices) to any ingredients in the meal replacement products, including lactose. * Previous scoliosis repair. Non-LED Qualitative Interview only participants * HbA1C greater than 80mmol/mol. * Presence of diabetes-related autoantibodies, as per local centre guidelines. * Confirmed mono-genetic cause of obesity (e.g. SIM1 mutation) or diabetes-associated syndrome such as Prader-Willi syndrome, Bardet-Biedl or Wolfram's syndrome. * Secondary diabetes (post bone marrow transplant/chemotherapy). * Significant psychiatric co-morbidity. * Breastfeeding, pregnant or planning to conceive during the LED and FR phases (female participants will be advised on need for effective contraceptive methods during the 12-month study period, section 5.1.1.10). * Any other condition which, in the opinion of the study investigator, would either make it inappropriate to undertake a period of LED. (All reasons for not approaching patients will be recorded and analysed anonymously. Cases can be discussed with the core study group if there is doubt). * Participation in another interventional trial within 6 months. * Informed consent and/or assent not received. * Pre-existing retinopathy. * Dietary avoidance (including, but not limited to, due to allergies, intolerances, religious reasons and lifestyle choices) to any ingredients in the meal replacement products, including lactose. * Previous scoliosis repair. HCPs • None.