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The notion that it’s possible to be obese and healthy finally may have been debunked.

While some obese people show no signs ofheart disease, a new study suggests it’s just a matter of time before the consequences of carrying substantial, excess pounds ultimately take a toll.

British researchers followed more than 2,500 men and women for 20 years, tracking their body mass indices (BMI), cholesterol counts, blood pressures, fasting glucose amounts and insulin resistance levels. Among many of the study subjects who were obese, heart disease risk factors eventually appeared, according to the study, published Monday in the Journal of the American College of Cardiology.

“Based on this the state of healthy obesity should be regarded as a high risk state,” said lead author Joshua Bell, a researcher in the department of epidemiology and public health at University College London in England. “Over the long term there is a tendency to progress to unhealthy obesity rather than staying stable or becoming healthy non-obese.”

The findings would appear to refute long-standing arguments that people can be obese and remain completely healthy.

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Bell and his colleagues defined “healthy obesity” as obesity with no metabolic risk factors for heart disease.

But over the course of 20 years, there was a trend for the “healthy obese” subjects to develop those risk factors, which include high blood pressure, diabetes and high cholesterol. By the end of the study, more than 51 percent had moved into the unhealthy category.

People with a BMI score of 30 or greater are considered "obese," according to this body-mass calculator offered by the National Institutes of Health. People with BMIs of 25 to 25.9 are classified as "overweight."

As for the other 48 percent, “you need to pay attention to the trend,” Bell said. “Twenty years is a long-time follow-up for research purposes, but it’s by no means a full-life course. The trend is for increasing numbers of the healthy obese people to become unhealthy obese. There may well be people who maintain stability over a lifetime, but we are talking about a small group of people. This doesn’t seem to be the norm, but rather the exception.”

At the study’s outset, 181 study participants were classified as obese, with 66 of those people designated as healthy. After five years, 32 percent of the “healthy obese” people had developed risk factors and at 10 years, 41 percent had been reclassified as unhealthy obese.

“I think that we Americans all want someone to confirm the idea that being obese is not all bad all the time,” said Dr. Kathryn Berlacher, an assistant professor in the University of Pittsburgh School of Medicine and a cardiologist at the school's Magee-Womens Hospital.

And while there may be a very small percentage of the population that can maintain good health while obese, “the large majority won’t be able to achieve that over the long term,” Berlacher said.

Dr. Andrew Freeman compares the developing science examining obesity to past findings on cigarette smoking.

Just as experts long ago documented the damage cigarettes can do in pack-years, modern researchers must assess the toll extra pounds take over time, said Freeman, director of clinical cardiology at National Jewish Health Medical Center in Denver.

The longer a person carries all of those extra pounds, the more potential there is for serious health damage, Freeman said.

“Obesity affects virtually every organ in the body,” Freeman added. “Fat itself is hormone secreting tissue. This article suggests that the longer you are obese, the less likely it is that you will stay healthy.”