We are doomed! The numbers are in, and as large as Americans are these days, they’re not done growing. Some 36 percent of American adults are considered obese. At a recent convention held by the U.S. Centers for Disease Control and Prevention, Duke University health economist Eric Finkelstein said that this figure is rising: Obesity prevalence among American adults is projected to rise to 42 percent by 2030.

Finkelstein’s numbers are based on findings collected from 1990 through 2008 as part of the Behavioral Risk Factor Surveillance System. There is some good news: Obesity-prevalence trends have slowed. Were the trends over the last 30 years still holding today, then by 2030 more than half (51 percent) of American adults would be obese. And then there’s the very bad news: The prevalance of severe obesity among adults will likely rise 130 percent by 2030.

What’s the problem? Carson Chow, a mathematician and investigator at the National Institute of Diabetes and Digestive and Kidney Diseases, told The New York Times that applied mathematics can render answers about the obesity epidemic much faster than clinical studies. His model shows that changes in agricultural policy and technology have made available more than 1,000 extra calories for the average American every day.

What can designers do about it? Chow says that it takes three years for a dieter to reach a new equilibrium (doomed!). But through evidence-based design and other strategies, architects and planners can build toward change. In May, AIA New York held its annual Fit City conference to discuss ways that design can promote physical activity . Curbing the obesity epidemic may be slow work, but architects can make changes that last.