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.

Kansas is predicted to go from a 30 percent rate of obesity to 62 percent.   Mississippi is expected to retain its crown as the fattest state in the nation for at least two more decades.

The new projections were released Tuesday by Trust for America’s Health with funding from the Robert Wood Johnson Foundation.

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 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 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.

By 2030, medical costs from treating obesity-related diseases are likely to increase by $48 billion, to $66 billion per year, his report said.