NEW YORK — We Americans already know how fat we are. Can it get much worse?

Apparently, yes, according to an advocacy group that predicts that by 2030 more than half the people in the vast majority of states will be obese.

Mississippi is expected to retain its crown as the fattest state in the nation for at least two more decades. The report predicts 67 percent of that state’s adults will be obese by 2030; that would be an astounding increase from Mississippi’s current 35 percent obesity rate.

The new projections were released Tuesday by Trust for America’s Health and the Robert Wood Johnson Foundation. The two organizations regularly report on obesity to raise awareness, and they rely 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 every state would have rates above 44 percent by that time, although it didn’t calculate a 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 for America’s Health officials said their projections are based in part on state-by-state surveys by the Centers for Disease Control and Prevention from 1999 through 2010. 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.

Officials with Trust for America’s Health said they believe their projections are reasonable.

“If we don’t do anything, I think that’s a fair prediction,” said Dr. Thomas Farley, health commissioner in New York City, which just passed a regulation banning supersize sugary drinks to curb obesity.

Trust for America 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 currently is in the middle of the pack when it comes to 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 for America’s Health 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, escalating 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 increase by $48 billion, to $66 billion per year, his report said.

The focus of so much of the ongoing debate about health care is over controlling costs, Levi said. “... We can only achieve it by addressing obesity. Otherwise, we’re just tinkering around the margins.”

———

Listed are 2011 obesity levels followed by the Trust for America’s Health projections for 2030. States are listed in order from the highest  to lowest projections in 2030:

Mississippi, 35 percent, 67 percent

Oklahoma,  31 percent,  66 percent

Delaware,  29 percent, 65 percent

Tennessee,  29 percent, 63 percent

South Carolina, 31 percent, 63 percent

Alabama, 32 percent, 63 percent

Kansas, 30 percent, 62 percent

Louisiana, 33 percent, 62 percent

Missouri, 30 percent, 62 percent

Arkansas, 31 percent, 61 percent

South Dakota, 28 percent, 60 percent

West Virginia, 32 percent, 60 percent

Kentucky, 30 percent, 60 percent

Ohio, 30 percent, 60 percent

Michigan, 31 percent, 59 percent

Arizona, 25 percent, 59 percent

Maryland, 28 percent, 59 percent

Florida, 27 percent, 59 percent

North Carolina, 29 percent, 58 percent

New Hampshire, 26 percent, 58 percent

Texas, 30 percent, 57 percent

North Dakota, 28 percent, 57 percent

Nebraska, 28 percent, 57 percent

Pennsylvania, 29 percent, 57 percent

Wyoming, 25 percent, 57 percent

Wisconsin, 28 percent, 56 percent

Indiana, 31 percent, 56 percent

Washington, 27 percent, 56 percent

Maine, 28 percent, 55 percent

Minnesota, 26 percent, 55 percent

Iowa, 29 percent, 54 percent

New Mexico, 26 percent, 54 percent

Rhode Island, 25 percent, 54 percent

Illinois, 27 percent, 54 percent

Georgia, 28 percent, 54 percent

Montana, 25 percent, 54 percent

Idaho, 27 percent, 53 percent

Hawaii, 22 percent, 52 percent

New York, 25 percent, 51 percent

Virginia, 29 percent, 50 percent

Nevada, 25 percent, 50 percent

Oregon, 27 percent, 49 percent

Massachusetts, 23 percent, 49 percent

New Jersey, 24 percent, 49 percent

Vermont, 25 percent, 48 percent

California, 24 percent, 47 percent

Connecticut, 25 percent, 47 percent

Utah, 24 percent, 46 percent

Alaska, 27 percent, 46 percent

Colorado, 21 percent, 45 percent

District of Columbia, 24 percent, 33 percent