Vascular and Metabolic Effects of Vitamin D Supplementation Associated With Lifestyle Management in Obese Adolescents

The main objective of this study is to analyze in a population of obese adolescents, the effect of vitamin D3 supplementation in addition to lifestyle and dietary management on vascular function assessed by the change between M0 and M3 of endothelium-dependent vasorelaxation measured at the brachial artery (Flow-Mediated Dilation).

The secondary objectives of this study are:

A. To analyze in obese adolescents, the effect of the addition of vitamin D3 supplementation on metabolic and vascular function.

B. To compare the relationships between food intake, metabolic, inflammatory, oxidative stress and vitamin D status, and vascular dysfunction between obese and normal weight subjects.

C. To evaluate the effects of sun exposure variations on relationships described in Objective B by comparing the observed parameters at baseline and at the end of the three month follow-up period, in non-supplemented obese adolescents and adolescents of normal weight.

D. To identify biomarkers (metabolic signatures) in obese adolescents associated with vitamin D deficiency and vascular function.

E. To evaluate in obese adolescents, the effects of vitamin D supplementation on the metabolome (metabolic signature).

F. To evaluate the effects of lifestyle and dietary management on these biomarkers (in the "control group").

For these targets (A to F), all teenagers will be classified according to three levels of skin pigmentation.

G. Establish a biobank of samples taken at baseline and at 3 months.

Eligibility Criteria:
General Inclusion Criteria:

* The patient's legal representatives must have given their informed and signed consent
* The patient must be insured or beneficiary of a health insurance plan
* Sexual maturation of at least Tanner stage 2

Inclusion criteria for the patient population

* The subject has a body mass index corresponding to grade 2 obesity according to the curves described by Rolland-Cachera et al (1991)
* Absence of at least 5% of total weight over the last 3 months

Inclusion criteria for the control population

* The subject has a body mass index \< 90th percentile

Exclusion Criteria:

* The patient is participating in another study
* The patient is in an exclusion period determined by a previous study
* The patient is under judicial protection
* The patient's legal representative(s) refuse(s) to sign the consent
* It is impossible to correctly inform the patient or his/her legal representative(s)
* The patient has a contraindication for physical activity (joint, heart or other)
* The subject does at least 3 hours of extracurricular physical activity per week
* The subject has a concomitant illness, a history of first-degree cardiovascular disease, abnormal glucose tolerance (pre-diabetes or diabetes).
* Active smoking
* Known dyslipidemia (particularly hypercholesterolemia).
* The subject regularly takes food and vitamin supplements and refuses to stop taking these during the study (in case of disruption of these supplements, a wash-out stopping period of 3 weeks is required).
* BMI corresponding to a grade 1 obesity according to the Rolland-Cachera et al. (1991) curves.
* Secondary or known genetic obesity.
* Known hypersensitivity to vitamin D.
* Hypercalcemia, hypercalciuria, calcium lithiasis