Members of the baby boomer generation are in worse health than their parents were at the same stage of life, with obesity and lack of exercise taking a toll, according to a new study.

About 13 percent of baby boomers — the generation born in the two decades after World War II — reported being in “excellent” health in middle age. That compares with 32 percent of the previous generation who said the same thing at the same stage of life, researchers reported in JAMA Internal Medicine.

“The baby boomer generation has a reputation of being active,” said Dana King, a professor at the West Virginia School of Medicine and the study’s lead author. But “that did not seem to jibe with what we’re seeing in our medical offices.”

King and his colleagues used data from an ongoing national health and nutrition survey to compare the answers of people who were 46 to 64 years old between 1988 and 1994, and the baby boomers who were in the same age range between 2007 and 2010.

Overall, about 39 percent of boomers were obese, compared with about 29 percent of the previous generation. Baby boomers were also less likely to get regular exercise.

About 16 percent of baby boomers had diabetes, compared with 12 percent of the previous generation. And baby boomers were more likely to have high cholesterol and high blood pressure.

King and his colleagues also found that baby boomers were more than twice as likely as people from the previous generation to use a cane or walker.

“I was surprised by the magnitude of the change. I suspected the current baby boomers would be not much healthier or maybe the same, but I didn’t expect them to have such a big change in disability and obesity,” King said.

But the news wasn’t all bad. King and his colleagues found that boomers don’t smoke as much as the previous generation and are less likely to have the lung disease emphysema. They were also less likely to have had a heart attack.

King said previous research has shown that baby boomers are known to live longer than earlier generations, but that may be a mixed blessing.

“You live longer, but those extra years you bought — you’re sick,” he said. “That’s not a good public health outcome.”

While the study doesn’t explain why baby boomers seem to be in worse shape than their predecessors, King thinks it shows they sit more and don’t exercise.

“It’s not too late to adopt new healthy lifestyle habits and make a big difference in your health,” he said.

“It really needs to have a high priority in your personal life. People should just do everything they can to be active and eat healthy. It would make such a dramatic difference.”