An estimated 1.2 billion adolescents – one in five people – live in the world today. In other words, approximately 20% of the total world population is made up of adolescents (WHO, 2005). They are the adults of tomorrow and their health is a fundamental issue for a healthy society in the future. However, the prevalence of overweight and obesity has increased significantly among young people since the 1980s worldwide (Haug, Samdal, Morgan, Ravens-Sieberer, & Currie, 2006). Over the past 20 years, the prevalence of obesity and overweight has increased at an alarming rate not only in developed countries but throughout the world (Worobey, 2006, chap.15). The increase in the prevalence of obesity has recently led the World Health Organization (WHO) to speak of a “global epidemic” to describe the problem of obesity (Tremblay and Doucet, 2000). I explained the prevalence of obesity at two levels: globally and in Iran.1.1.1.1 WorldwideAccording to a fact sheet published by WHO (2006) and the latest estimates from the International Obesity Taskforce (Taskforce, 2010), approximately 155 million school-age children are currently overweight or obese worldwide. Countries around the world have experienced a dramatic increase in the prevalence of overweight and obese children and adolescents over the past three decades (Bundred, Kitchiner, & Buchan, 2001; Ramachandran, et al., 2002; Baratta, Degano, Leonardi, Vigneri and Frittitta, 2006; Statistics obtained from various studies carried out in the European region (WHO, 2005) estimate that 10 to 30% of European schoolchildren aged 7 to 11 years and 8 to 25% of adolescents (14 to 17 years) face a excess body fat. Data from the United States and some European countries suggest that this increase...... middle of article...... l., 2008). A study conducted to compare the problem of childhood obesity in Middle Eastern countries found that different age groups showed a stable increase in the prevalence of overweight/obesity with age, with being male and higher socio-economic status (Mimiran, Sherafat-Kazemzadeh, Jalali -Farahani, & Azizi, 2010). In Iran, a country located in the Middle East, an increasing prevalence of overweight and obesity has been accompanied by an accelerated epidemiological and nutritional transition (Maddah, 2007; Malekzadeh, Mohamadnejad, Merat, Pourshams and Etemadi, 2005). Although the prevalence of obesity among Iranian adolescents is lower than that of developed countries like the United States, studies have shown a relatively high prevalence of obesity among Iranian youth in recent years, with obesity being the number one nutritional problem in Iran (Malekzadeh et al.. 2005).