In the present study the investigators will examine the impact of varying information (positive compared to standard information) concerning a drink for improving physical fitness in overweight children.

The present study will explore the short and medium term effects of receiving information concerning a drink (water) (positive compared to standard information) on the physical fitness in overweight children.

Study subjects will be 30 overweight children aged 6 to 13, new participates in a nutritional, behavioral sport program,The control group of 30 normal weight children.

The first stage of the study the investigators will examine the short-term influence of different types of information concerning water on subjects' fitness which will be measured by treadmill performance. First, the water will be presented to the participants children as an ordinary water while in the second case it will be presented as an "energy drink".

The second stage of the study will examine the impact of varying information on the subjects' sports participation/level of physical activity over a 6 week period of training, Study subjects will be 30 over-weight children aged 6 to 13, who participate in a nutritional, behavioral sport program. During this period, information on the type of drink will be changed every week. Children will be assessed in all training sessions and their level of activity will be monitored to examine whether the information on the drink led to a different exercise behavior.

The study hypothesis is that the use of these positive information will increase participants' fitness and levels of activity compared to standard information.

Inclusion Criteria:

• Pre pubertal children
• Study group: BMI precentiles over 85 (overweight and obese children)
• Control group: BMI precentiles between 5-85 (normal weight children)

Exclusion Criteria:

• Children with organic Disease
• Competitive athlete

Subjects will be given the same drink (water) in different packaging