Metformin Intervention in children and adolescents with obesity. A parallel, three arms, randomized, 6 months, multi-center study with metformin extended release (XR) plus lifestyle or metformin immediate release (IR) plus lifestyle or lifestyle alone.

Prior treatment

• Steroid treatment (oral or injected).
• Unstable treatment for neuropsychiatric disorders such as ADHD/ADD, and/or treatment started within 3 months prior to screening visit.
• Participation in another clinical study involving an Investigational Medicinal Product (IMP) within three months prior to screening.
• Total or partial gastric or small intestine resection.

Other illness

• Known syndromal obesity (e.g. Prader-Willi syndrome, Bardet-Biedl syndrome or Laurence-Moon syndrome).
• Chronic disease, as judged by investigator.
• Known hypersensitivity to metformin or any of the excipients.
• Indigestion-causing diseases.
• Severe gastrointestinal disease, as judged by investigator.
• Type 1 diabetes mellitus.
• Severe depression, severe anxiety or other psychiatric disorder referred to or undergoing special treatment, as judged by investigator.

Lab values

• Any concomitant medication influencing blood glucose (e.g. metformin and acarbose), influencing other parameters of metabolic syndrome (e.g. orlistat) or interfering with the investigational medicinal product from 3 months prior to screening until the end of the treatment period at visit 11.
• Kidney disease or renal dysfunction, acute or chronic (eGFR <60ml/min/1,73m2 ).

Other

• Severe sleep apnea, as judged by investigator.
• Antidepressants that can lead to weight gain, as judged by investigator.
• Language difficulties, impaired mental ability or not willing to understand or comply with the study procedures.
• Subject from the same household participating in this trial.
• Pregnancy or lactation.
• Hypo-/hyperthyroidism, unless stable treatment.

• Signed informed consent prior to any study-specific procedures.
• Males or females of age 6 to less than 17 years and 3 months at the time of signing informed consent.
• Body weight ≥ 40 kg.
• Obesity (BMI-SDS >2.0) according to WHO.
• Stable body weight during previous 90 days before screening visit 1 (< 5kg measured or self-reported weight change).
• If female of childbearing potential: Not sexually active or usage of adequate anticonception and having negative pregnancy tests. Methods that can achieve a failure rate of less than 1% per year (Pearl index <1), when used consistently and correctly, are considered as highly effective birth control methods. Such methods include: •Combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation: oral, intravaginal, transdermal. •Progestogen-only hormonal contraception associated with inhibition of ovulation: oral, injectable, implantable. •Intrauterine device (IUD). • Intrauterine hormone-releasing system (IUS). • Bilateral tubal occlusion. • Vasectomised partner. • Sexual abstinence (if refraining from heterosexual intercourse during the entire period of risk associated with the study treatments. The reliability of sexual abstinence needs to be evaluated in relation to the preferred and usual lifestyle).