Monthly Boluses Versus Daily Doses for Correcting Blood Vitamin D Deficit in Obese Children and Adolescents

Inclusion Criteria: * Aged between 5 to 18 year-old * Being obese (BMI \>97th percentile, \> IOTF 30, for age and gender using the WHO references) * Patients (parents) having given their informed consent * Patient having insurance from the national health system Exclusion Criteria: Children will be excluded from the study if: * Symptomatic vitamin D deficiency (tetany, muscular hypotonia, hypocalcaemic seizure) * Vitamin D supplementation in the 3 months preceding the inclusion visit (V1) * Signs of rickets at the X-ray (osteopenia and cortical thinning of the long bones, stress fractures, and metaphyseal widening and fraying) * Chronic disease such as granulomatous conditions, Williams syndrome, or hypothyroidism predisposing to hypocalcaemia or in case of hypercalcaemia (calcium \> 2.65 mmol/L), liver/kidney disease, malabsorption diseases; * Hypercalciuria (urinary Calcium/Creatinine \> 0.7 mmol/mmol), calcium nephrolithiasis, hypervitaminosis D (25-(OH)D \> 250 nmol/L); nephrocalcinosis; * Ongoing treatment with anticonvulsants/barbiturates or steroids which increase the catabolism of 25(OH)D; * Ongoing treatment with thiazides diuretics which reduce urinary excretion of calcium; * Contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to class of drugs or the investigational product; * Pregnancy, breastfeeding; * Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant; * Simultaneous enrolment to another study which could influence the results of the current study; * Patient under legal protection or deprived of liberty.