Effect of Docosahexaenoic Acid Supplementation on Microbiome in Obese ChiLdrEn.

Evaluation of the possible effect of DHA supplementation, combined with interventions aimed at improving diet and lifestyle, on gut microbiota composition and metabolite production.

Differences in gut microbiota composition and function will be evaluated in obese children before starting the DHA supplementation and dietary-lifestyle intervention, at the end of DHA supplementation (4 months) e after 4 months of dietary dietary-lifestyle intervention without DHA supplementation. The investigators will identify the role of DHA on the intestinal microbiota and indicative species related to insulin resistance (IR). The investigators will determine whether DHA supplementation, combined with interventions to improve diet and lifestyle, reduces adverse metabolic consequences together with their co-morbidities.

The following tasks will be also performed at t0, t1 and t2:

Clinical examination including: physical examination, Tanner score evaluation; Bristol Stool Chart Blood pressure will be checked in all children by using oscillometric devices validated in the pediatric age group.

Anthropometry including body circumferences and skinfolds, calculation of BMI z scores and body composition. Body composition will be assessed using an air displacement plethysmography system (BOD POD COSMED-USA).

Dietary assessment:

* Food intakes will be recorded by prospective 3-d weighed food records obtained with food scales. Parents will be advised on how to record all food and beverages consumed during 2 weekdays and 1 weekend day. Quantification and analysis of the energy intake and nutrient composition will be performed with an ad hoc PC software (MètaDieta®, Me.Te.Da S.r.l., San Benedetto del Tronto, Italy).
* Mediterranean Diet Quality Index (KIDMED) questionnaire for Mediterranean Diet assessment. The KIDMED index ranges from 0 to 12, and is based on a 16-question test that can be self-administered. The sums of the values from the administered test will be classified into three levels:

  8 or more: optimal Mediterranean diet; 4-7: improvement needed to adjust intake to Mediterranean patterns. 3 or less: very low diet quality.

Hematological and biochemical status including:

Complete cell blood count;

Metabolic and nutritional parameters according to local routines for childhood obesity (fasting glucose, fasting insulin, LDL, HDL, total cholesterol, triglycerides, Apolipoprotein A and Apolipoprotein B levels, transaminases and amma-glutamyl transferase). Oral Glucose Tolerance Test (OGTT) will be performed. The insulin sensitivity and insulin resistance was assessed by calculating HOMA index (Homeostasis Model Assessment) and QUICKI (Quantitative Insulin-Sensitivity Check Index), using the following formulas:

HOMA: fasting plasma insulin in mU/l x FPG in mmol/l/22.5 QUICKI: 1/(log10 fasting plasma insulin in mU/l + log10 glucose in mg/dl)

Inflammatory index (VES, high-sensitive CRP, including fecal calprotectin)

Liver ultrasonography for detection of fatty liver disease

Eligibility Criteria:
Inclusion Criteria:

* 6 \<Age \<14 years
* Severe obesity (\>3 DS) according to WHO classification.
* Gestational age: 37-42 weeks.
* Birth-weight: \> 2500 g e \< 4000 g
* Caucasian

Exclusion Criteria:

* secondary obesity
* supplementation with pre/probiotics (in the previous 3 months);
* antibiotic treatment (in the previous 3 months);
* chronic or acute intestinal diseases (in the previous 3 months).