The new projections were released Tuesday by Trust for America's Health with funding from the Robert Wood Johnson Foundation. The trust regularly reports on obesity to raise awareness, mostly relying on government figures.
The group's dismal forecast goes beyond the 42 percent national obesity level that federal health officials project by 2030. The group predicts that every state would have rates above 44 percent by then, although it didn't calculate an overall national average.
About two-thirds of Americans are overweight now. That includes those who are obese, a group that accounts for about 36 percent. Obesity rates have been holding steady in recent years. Obesity is defined as having a body-mass index of 30 or more, a measure of weight for height.
Trust officials said their projections were based in part on state-by-state surveys from 1999 through 2010 by the Centers for Disease Control and Prevention. The phone surveys ask residents to self-report their height and weight; people aren't always so accurate about that.
The researchers then looked at other national data tracking residents' weight and measurements and made adjustments for how much people in each state might fudge the truth about their weight. They also tried to apply recent trends in obesity rates, along with other factors, to make the predictions.
Trust officials said they believed that their projections were reasonable. And New York City's health commissioner agreed. "If we don't do anything," said Thomas Farley, a physician, "I think that's a fair prediction." His city recently banned supersize sugary drinks.
The trust projects that by 2030, 13 states would have adult obesity rates above 60 percent, 39 states might have rates above 50 percent, and every state would have rates above 44 percent.
Even in the thinnest state - Colorado, where about one-fifth of residents are obese - 45 percent would be obese by 2030.
Perhaps more surprising, Delaware is expected to have obesity levels nearly as high as Mississippi. Delaware now is in the middle of the pack in self-reported obesity rates.
The report didn't detail why some states' rates were expected to jump more than others. It also didn't calculate an average adult obesity rate for the entire nation in 2030, as the CDC did a few months ago. But a researcher who worked on the trust's study acknowledged that report's numbers point toward a figure close to 50 percent.
CDC officials declined to comment on the new report.
Whichever estimates you trust most, it's clear that the nation's weight problem is going to continue, raising the number of cases of diabetes, heart disease, and stroke, said Jeff Levi, executive director of Trust for America's Health.
By 2030, medical costs from treating obesity-related diseases are likely to rise $48 billion, to $66 billion per year, his report said.
The ongoing debate about health care focuses on controlling costs, Levi said. " . . . We can only achieve it by addressing obesity. Otherwise, we're just tinkering around the margins."