In the United States, childhood obesity affects approximately 12.5 million children and teens (17% of that population). Changes in obesity prevalence from the 1960s show a rapid increase in the 1980s and 1990s, when obesity prevalence among children and teens tripled, from nearly 5% to approximately 15% (Figure 1). During the past 10 years, the rapid increase in obesity has slowed and might have leveled. However, among the heaviest boys, a significant increase in obesity has been observed, with the heaviest getting even heavier. Moreover, substantial racial/ethnic disparities exist, with Hispanic boys and non-Hispanic black girls disproportionately affected by obesity (Figure 2). Also, older children and teens are more likely to be obese compared with preschoolers.