This study evaluates the effect of an interventional model for preventing and controlling overweight and obesity in male and female fifth-graders. First, based on WHO (World Health Organization) references obese (BMI-Z score ≥ 2) and overweight (BMI-Z score ≥ 1) students from 12 primary schools (randomly allocated to 6 intervention and 6 comparison) will be screened. Then from the screened students 30 students with the following inclusion criteria will be recruited: not metabolically ill, not on a weight losing diet and not professionally athlete. For selected students BMI-Z score as primary outcome will be calculated. Demographic data, as well as data on waist and hip circumference, triceps skin-fold thickness, food intake for 3 days (2 ordinary week days and 1 weekend) and physical activity will be collected at the beginning and at end of the 6-month intervention. The approach of the study will be Health Promoting Schools. The intervention includes three components, i.e., nutrition education (students and parents), increased physical activity, and changing environment (food items offered in schools' canteens). Nutrition education will be imparted (a 30-minute session per week) by health instructors; physical activity will be done under the supervision of the school coaches (2 one-hour sessions per week). Parents' education (a 1.5-hour session) will be monthly. Finally the efficacy of the intervention will be determined and reported.

Inclusion Criteria:

• BMI-Z-Score> or =1 (WHO)
• Students in the fifth or sixth grades

Exclusion Criteria:

• Metabolic disorders (hypo or hyperthyroidism)
• Any disease which interfere with adherence to the intervention
• Intake of any appetite-reducing drug
• Doing professional sports
• Being on a weight reduction diet