Obesity

American culture values thinness. From supermodels to laptop computers, the American public equates thinness with beauty; yet, the prevalence of obesity in the United States is higher than at any time in history. Estimates of overweight and obesity among children and adolescents in the United States have doubled since the 1970s, to almost 25 percent in 2001. Once obesity develops in childhood or adolescence, there is a risk that it will persist into adult life. The risk appears to be greatest for children who are obese in the prepubertal years (between ages nine and thirteen), with more than 50 percent of such children remaining obese as adults, and for children with one or two obese parents.

William Dietz, of the Centers for Disease Control and Prevention (CDC), described three critical periods in the development of obesity, corresponding to periods of adipose tissue (the connective tissue where fat is stored) proliferation: gestation and early infancy, ages five to seven years, and adolescence. Body fat increases over the first twelve to eighteen months of life. Loss of "baby fat" over the subsequent eighteen months leads to a decrease in fatness, which lasts until the age of five to seven years, when the adiposity rebound occurs and fatness begins to increase again. Children who experience the adiposity rebound earlier, before five years and six months of age, are more prone to later obesity.