The primary purpose of this protocol is to assess the hormonal regulation of satiety by an intense exercise before and after a 3 month physical activity program. Hormones assessed are: leptin, grhélin, Cholecystokinin, Glucagon-Like-Peptid-1 (GLP-1), PYY.

It is well known that in overweight adults and children also, an intense physical exercise diminish the food intake relatively to the total energy expenditure and this effect is persistent after a 6 weeks physical activity program.

Our hypothesis are: a diminution of food intake after the intense physical exercise and a persistent diminution of food intake after the 3 month physical activity program, an augmentation of levels of GLP-1 and PYY during the intense exercise before and after the physical activity program, a diminution of the level of GLP-1 and leptin before and after the physical activity program

There is two sequences, one before and one after the physical activity program. Each sequence contains one "rest" session and one "exercise" session.

Each session contains : blood sample at regular interval (Leptin, Ghrélin, CCK, PYY, GLP-1), a sleeping assessment (Pittsburg scale), an assessment of hunger sensations at regular interval, an assessment of food intake in a "ad libitum" lunch and in the diner indirectly by the SU.VI.MAX. tool.

During the " rest " session :

Blood samples, assessment of hunger sensation, assessment of food intake are realized during the morning. Physical condition (VO2 max, DEXA, and muscular test), insulin-sensibility, lipid profile, are also assessed.

During the "exercise" session: it is identical to the first session but an intense exercise of 40 minutes is realized at 70% of the patient's VO2 max. The peripherical blood output is measured by a non-invasive method: the Near-Infra-Red-Spectroscopy, during the exercise.

The 3-months-physical activity program : there is 4 sessions of 30 minutes and 2 sessions of 1 hour per week. Most of exercises sessions are realized at home but one 1-hour session per week is controled with a sports educator.

Inclusion Criteria:

Overweight adolescents (over the 90 th percentile of the international cut-off point)

• With a computer and an internet connection
• Sedentary (according to the IPAQ-A questionnaire)
• Without eating disorders (according to the DEBQ questionnaire)

Exclusion Criteria:

• Medical or surgical antecedents that are incompatible with the study: cardiovascular, endocrine or digestive disease.
• Drugs that could interfere with the results of the study
• Surgical intervention in the 3 months
• Regular consumption of tobacco or Alcohol
• patients on a diet with caloric restriction
• Refusal to sign the consent form
• Regular practice of sport and intensive