The idea that people can be obese and still be "healthy" is called into question by a new study, that finds that, at least over the long term, obesity itself may confer a small increased risk of death.
In the study, people who were obese but did not have metabolic problems — meaning they had normal blood pressure, cholesterol, blood sugar and other measures of metabolic health — were still 24 percent more likely to experience a heart problem, such as a heart attack, or die from any cause over a 10-year period, compared with people who were a normal weight and also had no metabolic problems.
The results "demonstrate that there is no 'healthy' pattern of obesity," said the researchers, from Mount Sinai Hospital in Toronto. [7 Medical Myths Even Doctors Believe]
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In an editorial accompanying the study, James Hill and Dr. Holly Wyatt, of the University of Colorado, said the findings are consistent with the idea that obesity itself is a disease, a controversial issue that the American Medical Association supported this year.
However, some experts disagree with the researchers' conclusions. Dr. Pieter Cohen, an assistant professor of medicine at Harvard Medical School and a general internist at Cambridge Health Alliance in Boston, stressed that the effects of metabolic conditions like high blood pressure and high cholesterol are "much more important for long-term heart health than one's weight."
Obese but 'healthy'?
Research on whether people can be obese and healthy has had contradictory results. A study published earlier this year found that people who are overweight actually live longer than people who have normal weights.
In the new study, the researchers analyzed information from eight previously published studies involving more than 61,000 people, most of whom were in their 40s and 50s. Just how long researchers followed participants varied depending on the study, from 3 to 30 years. About 9 percent of participants were obese but metabolically healthy.
Overall, people who were metabolically unhealthy — with conditions such as high blood pressure, high cholesterol or diabetes — were at increased risk of heart problems or death during the study period, regardless of whether they were of normal weight, overweight or obese.
When the researchers considered only studies that followed participants for at least 10 years, they found that, even with no metabolic problems, obese people were still at increased risk for heart problems or death during the study period.
Criticism
Cohen said he would have interpreted the results differently.
"How [the authors] represent their results … doesn’t at all reflect, in my opinion, what they found in the study," Cohen said.
Cohen pointed out that, according to the study data, just one out of 140 "healthy" obese people would be expected to die or have a heart problem over a 10-year period.
"I would look at the glass completely full, in that, if your metabolic panel is great, obesity itself confers an extremely small risk of heart disease," Cohen said.
The researchers said that, when applied to the worldwide population, their findings translate to 1.4 million deaths or heart problems over a decade.
Cohen said that while the researchers followed participants for at least 10 years, information about participants' metabolic status was collected just once. So even among the 1 in 140 healthy obese who are at increased risk of death or heart problems, it's unclear if that risk should be attributed to obesity itself, or a worsening metabolic condition that was not captured by the study, Cohen said.
The study was not able to take into account how much physical activity participants engaged in, which could have also affected their risk of death.
However, Cohen said that, because obesity itself can increase the risk of joint problems such as damage to the hips and knees, it is still advisable for obese people to lose weight, even if they are metabolically healthy.
The study will be published Dec. 3 in the journal Annals of Internal Medicine.
Follow Rachael Rettner @RachaelRettner. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.
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