The investigators hypothesize that Metformin decreases weight, normalizes lipid profile and increases insulin sensitivity; the study team hope to get better effect of weight decrease and metabolic processes repair in the intensive treatment group with intervention of physical activity, diet correction and Metformin use.

During the first visit, study participants would follow the clinical investigation (anthropometry, physical examination, blood tests (hormonal and biochemical state), bioimpedance, ultrasound evaluation) and be attributed into 4 groups (matched for age, gender, pubertal stage and BMI), 100 subjects in each group.

1. st group - control: during the first visit patients get standardized information on healthy lifestyle, diet and exercise. Next visit (control) will be scheduled for the clinical and laboratory evaluation after 12 months of intervention.

2. nd group - intensive diet and physical activity group: Children will be seen

   1. by a dietician once a month for diet re-evaluation;
   2. physical therapist, who will give physical activity course twice a week (1 h each).
   3. pediatric endocrinologist every 3 months. Clinical and laboratory evaluation after 12 months of intervention.

3. rd group - intensive diet and physical activity group plus insulin sensitization: Metformin will be prescribed for this group of study children in the doses of 1000 mg/day Children will be seen by

   1. a dietician once a month for diet re-evaluation;
   2. physical therapist, who will give physical activity course twice a week (1 h each);
   3. pediatric endocrinologist every 3 month. Clinical and laboratory evaluation after 12 months of intervention.

4. th group- insulin sensitization without intensive diet and physical activity. Metformin will be prescribed in the doses of 1000 mg/day after standardized information on healthy lifestyle, diet and exercise during the first visit only. This group of children will be seen by pediatric endocrinologist every 3 months.

Intervention duration - 12 months. In the case of Metformin intolerance, children will continue the study in 2nd group.

Clinical and laboratory evaluation after 12 months of intervention.

Inclusion Criteria:

• Age 10-17 yrs;
• Weight > 85th percentile for age and gender (by IOTF);
• Living in Kaunas and its region;
• No obvious chronic diseases;
• Not on steroid or other long-term treatment;
• Informed consent of the patient and parents (official caregivers);

Exclusion Criteria:

• Age less than 10 or above 17 yrs;
• Diagnosis of type 1 diabetes;
• Chronic illness that may affect physical activity and metabolic profile;
• Insulin treatment;
• Steroid treatment;
• Planning to move from Kaunas or its region in the period of 1 year;
• Protocol refused by the patient or his parents;

Study results are in progress with statistical analysis