For the past several years, health experts have toyed with the theory of "healthy obesity," claiming that some people can be perfectly healthy while still maintaining a weight that the charts would indicate as obese. But a new study debunks this notion, with data showing that for the majority of people, good health and obesity cannot coincide.

Researchers at the University College London examined what they called the "obesity paradox," that claimed that for some people obesity could improve their long-term chances of survival with illnesses such as heart disease. The theory behind this paradox stems from previous studies that have found that some overweight people do not suffer from obesity-related health issues such as high blood pressure, bad cholesterol and elevated blood sugar. In fact, for some, obesity seemed to actually ward off these related diseases. Health experts theorized that the extra weight gave some people extra energy stores that they could draw from to fend off illness.

To test this theory, researchers tracked the health patterns of more than 2,500 British men and women over a twenty year period — the longest study of its kind. They measured each participant's body mass index, cholesterol, blood pressure and blood sugar levels and categorized them as either healthy or unhealthy and obese or non-obese. Their results were published in the recent issue of the Journal of the American College of Cardiology.

About one-third of the obese people were considered "healthy obese," as they had no risk factors for chronic disease at the beginning of the study. But over time, this group began to succumb to the risk factors for chronic disease. At the 10-year mark, 40 percent of those considered "healthy obese," now fell into the unhealthy obese category. After 20 years, 51 percent of this group were now considered unhealthy.

Bottom line: Researchers found that, over time, most people who are overweight or obese face a higher risk of heart attack, stroke and certain kinds of cancer than those who maintain a so-called "normal" weight.

"Healthy obesity is something that's a phase rather than something that's enduring over time," said Joshua Bell, a doctoral student in University College London's department of epidemiology and public health and a lead author of the study. "It's important to have a long-term view of healthy obesity, and to bear in mind the long-term tendencies. As long as obesity persists, health tends to decline. It does seem to be a high-risk state."

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'Healthy obesity' is a myth, study finds
While some obese participants initially appeared healthy, researchers found that over time, they were at higher risk for chronic disease than their peers.