Low-energy diet program for teens with obesity and type 2 diabetes (LEGEND)

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.