Obesity, defined as a body mass index of 30 or greater, is an epidemic in the United States and other industrialized nations, and it is rapidly becoming one in developing nations. As countries transition to westernized lifestyles, obesity tends to increase. Obesity rates vary from as little as 2 percent in some Asian countries to as much as 75 percent in some Pacific nations. There are more than 300 million obese persons in the world, and more than 750 million overweight persons. In the United States, 34 percent of adults are overweight and 30.5 percent are obese. Between 1980 and 2000, the percentage of overweight children aged six to eleven doubled, from 7 percent to 15 percent, and the percentage of overweight adolescents ages twelve to nineteen tripled, from 5 percent to 16 percent. In Europe, the thinnest country is Sweden, with about 10 percent obesity, while the fattest is Lithuania, with about 79 percent obesity. The sad fact is the prevalence of obesity appears to be increasing in all countries.