Within 10 years, nearly half of American adults will be obese—or very overweight—a new report predicts.

In addition, the researchers warned that one in four Americans will be severely obese.

The new report used a federal study that lasted more than 20 years and included data from 6.3 million adults. The researchers made predictions for the future based on current trends.

Their study corrects for a weakness in earlier studies. Before, research usually depended on national health surveys in which people often reported their weight as less than it really was.

"It's alarming," said nutrition expert Dr. Lawrence Appel of Johns Hopkins University. He was not involved in the study. "We're going to have some pretty awful problems" medically and financially because so many people weigh too much, he said.

The New England Journal of Medicine published the study in December. It was the result of work by researchers at Harvard and George Washington universities.

The chief writer of the study, Zachary Ward, is with Harvard T.H. Chan School of Public Health in Boston. He spoke about the findings with Reuters news service.

"Obesity is getting worse in every state," he said. "And especially concerning is severe obesity, which used to be pretty rare" and which now will be the most common group for a lot of states across the country.

Most affected will be women, blacks and low-income adults. The study said nearly one third of people in those groups will be severely obese.

Obesity can result in many health problems. The risk for heart disease, stroke, diabetes and cancer all go up when someone is severely overweight.

How is obesity measured?

Obesity is generally defined by a person's body mass index number, or BMI. This is the measure of weight compared to height. A BMI of 30 or greater is considered obese.

The Centers for Disease Control and Prevention (CDC) estimates that 40 percent of U.S. adults are obese.

The new research predicts that by 2030, about 49 percent of U.S. adults will be obese. In 29 states, more than half will be.

In addition, about one fourth will suffer severe obesity.

The study did not look at the reasons behind the increases, but "income is a big driver. Age is a big driver," Ward said. States with younger people have lower obesity rates because people usually "gain weight as they age."

The state with the lowest obesity rate will be Colorado, which has always had lower rates. Ward said people in Colorado do a lot of outdoor activities, and they may have higher income. He added that living at higher elevations, like Colorado might also influence the results. "There may be something about having to take a little extra energy to do everything at a higher altitude" that keeps weights lower, he said.

The study was paid for by the JPB Foundation, which studies poverty and problems in society.

However, there have been some other hopeful developments in the effort to limit obesity.

In June, the CDC reported decreasing obesity rates among the youngest school children on government food aid. Obesity among these children fell from 16 percent in 2010 to 14 percent in 2016.

I'm Anne Ball.

Anne Ball wrote this story with information from the Associated Press and Reuters News Agency. Mario Ritter, Jr. was the editor.

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trend – n. a general direction of change : a way of behaving, or proceeding, that is developing and becoming more common

survey - n. an activity in which many people are asked a question or a series of questions in order to gather information about what most people do or think about something

alarm – n. a warning of danger

diabetes – n. a serious disease in which the body cannot properly control the amount of sugar in your blood because it does not have enough insulin

elevation – n. the height of a place

altitude – n. the height of something (such as an airplane) above the level of the sea