Global changes in diet and activity patterns are fueling the obesity epidemic, as obesity is reaching pandemic proportions throughout the world (World Health Organization (WHO), 1998). As the availability of fast, inexpensive, energy-dense foods grow and physical activity declines, obesity rates across all ethnic and age groups is projected to increase. Within England the rate of obesity has almost tripled in the last two decades and the statistics indicate that almost 20% of adults are classified as obese (National Audit Office, 2001a; Erens et al., 2001). The statistics with regards to obesity in children and adolescents are almost as profound as those for adult. In fact, the prevalence of obesity among children and adolescents has been rising at an astounding rate, nearly doubling over the past three decades, and has reached epidemic proportions. As of 2002, a reported 31.5% of youth were at risk for overweight and 16.5% could be classified as overweight (Medley, Ogden, Johnson, Carroll, Curtin, & Flegal, 2004).

The negative health consequences of obesity in children and adolescents are indisputable. When compared to children of normal weight, those who are obese are twice as likely to develop cardiovascular disease or hypertension and are three times as likely as their non-obese peers to develop diabetes as adults (Mossberg, 1989). Obese children also are at increased risk for dyslipidemia, both increased low-density lipoprotein levels and decreased high-density lipoprotein levels (Leung & Robson, 1990). Longitudinal data from the Bogolusa Heart Study indicates a significant risk for developing type 2 diabetes for obese adolescents (Srinivasan, Bao, Wattigney, & Berenson, 1996). Among those who were obese as adolescents, 2.4% had developed type 2 diabetes by the age of 30 compared to none in the non-obese population. The detrimental health effects of obesity are pervasive and enduring. Strauss (1999) reported that being an obese adolescent predicted early mortality even more consistently than obesity in adulthood.

The complications related to obesity in youths are not limited to physical health. Obesity in adolescents also has been associated with fewer years of education, higher poverty, lower marriage rates and lower family income (Dietz, 1997; Maffeis & Tato, 2001). However, evidence for an association between overweight and obesity and low self-esteem are inconsistent. Some studies have found no significant relationship (e.g., Gortmaker, 1993; Renman, Engstrom, Silfverdal, & Aman, 1999), while others find that those children and adolescents who are obese exhibit significantly lower self-esteem than their peers (French, Story, & Perry, 1995). Israel and Ivanova (2002) posit that severity of obesity is related to self-esteem with those more severely obese experiencing the most damage to their self-esteem. This hypothesis has been validated in the findings among clinical populations where self-esteem has been significantly related to obesity status (Rumpel & Harris, 1994). The most consistently replicated psychosocial outcomes for obesity relate to negative body image (Israel & Ivanvova, 2002). In addition, clinically significant problems with memory functioning and learning abilities have been found among overweight children (Rhodes et al., 1995). These deficits are seemingly the result of sleep apnea, which has been reported at rates as high as 94% among samples of obese children (Brenner, Kelly, Wenger, Brich, & Morrow, 2001).

As overweight and obesity among youths became a significant concern in the 1960s and 1970s, the development and evaluation of treatments became a popular area of inquiry (for examples of early clinical trials of obesity treatments for children, see Aragona, Cassady, & Drabman, 1975; Christakis, Sajecki, Hillman et al., 1966). As treatment options developed, qualitative reviews of the literature emerged that identified common themes that seemed to be efficacious in treatments including behavioral interventions (e.g., Epstein & Wing, 1987), diet programs (e.g., Ryttig, et al., 1989), exercise components (e.g., Sasaki, Shinko, Tanaka et al., 1989) and school based interventions (e.g., Lansky & Brownell, 1982). However, consensus on the effect size of these treatments remained obscure (Dietz, 1983; Spence, 1986).