About 4 in 10 American adults are obese, nearly 1 in 10 severely so, government researchers said Thursday.

The Centers for Disease Control and Prevention findings come from a 2017-18 health survey that measures height and weight. More than 5,000 U.S. adults took part.

The survey found that the obesity rate was 42%, higher than the 40% found in a similar 2015-16 study. The severe obesity rate was more than 9% in the new survey, up from the 8% figure in the previous one.

Those increases aren’t considered statistically significant: The survey numbers are small enough that there’s a mathematical chance the rates didn’t truly rise.

But it’s clear that adult obesity rates are trending up, said the CDC’s Cynthia Ogden, one of the report’s authors.

A half-century ago, about 1 in 100 American adults were severely obese. Now it’s 10 times more common.

The obesity rate has risen about 40% in the last two decades.

The findings suggest that more Americans will get diabetes, heart disease and cancer, said Dr. William Dietz, a George Washington University obesity expert.

It also will be increasingly difficult for doctors to care for so many severely obese people, Dietz said. He has estimated that on average, every primary care doctor treating adults has about 100 severely obese patients.

“How’s a provider going to do that? Severe obesity really requires very intensive therapy,” he said.

The CDC didn’t report new obesity numbers for kids and teens. That may come out later this year, Ogden said. In 2015-16, 18.5% of kids and teens were obese and just under 6% were severely obese.

Dietz faulted the government for not pushing for more measures to promote physical activity and better eating. Building more sidewalks and passing a national tax on sugary beverages could make a big difference, he said.

Obesity — which means not merely overweight, but seriously overweight — is considered one of the nation’s leading public health problems.

It is measured by the body mass index, or BMI, a figure calculated from a person’s weight and height. A BMI of 25 or greater is considered overweight, a BMI of 30 and above is obese, and a BMI of 40 or above is severely obese.

A person who is 5-foot-4, the average height for U.S. women, is considered obese at a weight of 174 pounds and severely obese above 232 pounds. A person who is 5-foot-9, about the average height for men, is deemed obese at 203 pounds and severely obese at 270.