In the post-apocalyptic 2008 cartoon movie WALL-E, the remaining humans have acquired the proportions of blubbery marine mammals and use levitating gurneys to get around. Given recent weight trends, it seems increasingly unlikely that such a scenario will materialize without the aid of computer animation.
The latest data from the National Health and Nutrition Examination Survey show that obesity rates among American children and adults have leveled off. Since 1999 the prevalence of high body mass index (BMI) among children and adolescents has been about 17 percent. Among women in the survey, the rate of obesity (defined as having a BMI of 30 or more) was about 33 percent from 1999 through 2004, rose slightly to 35 percent in 2005, and has held steady since then. Among men during the same period, the rate rose from 31 percent to 33 percent before declining to 32 percent.
"Right now we've halted the progress of the obesity epidemic," William H. Dietz, director of the Division of Nutrition, Physical Activity, and Obesity at the U.S. Centers for Disease Control and Prevention, told The New York Times in January. "The data are really promising." Dietz credited healthier food in schools and increased nutritional awareness with stopping the transition from man to manatee, saying mothers are "making changes for themselves that they're also making for their kids."
David Ludwig, director of the Optimal Weight for Life Program at Children's Hospital in Boston, is less confident that lifestyle changes account for the plateau. "It could be that most of the people who are genetically susceptible, or susceptible for psychological or behavioral reasons, have already become obese," Ludwig told the Times. Or it may be that "we've reached a biological limit" to how fat we can get; because people burn more calories to maintain and transport their bodies as they gain weight, he said, "a population doesn't keep getting heavier and heavier indefinitely."