NEW YORK, NEW YORK — If Americans stick to their eating and exercise habits, future historians will look back on the early 21st century as a golden age of svelte.

Using a model of population and other trends, a new report released on Tuesday by the Trust for America’s Health and the Robert Wood Johnson Foundation projects that half of U.S. adults will be obese by 2030 unless Americans change their ways.

The ‘F as in Fat’ report highlights the current glum picture of the U.S. obesity epidemic, in which 35.7 percent of adults and 16.9 percent of children age 2 to 19 are obese, as the Centers for Disease Control and Prevention (CDC) reported earlier this year.

But for the first time, the report builds on state-by-state data from the CDC to project obesity rates. In every state, that rate will reach at least 44 percent by 2030. In 13, that number would exceed 60 percent.

Obesity raises the risk of numerous diseases, from type 2 diabetes to endometrial cancer, meaning more sick people and higher medical costs in the future, the report said.

It projects as many as 7.9 million new cases of diabetes a year, compared with 1.9 million new cases in […]