For a small number of obese people, those extra kilos do not condemn them to heart disease or diabetes, Dutch researchers report.
For those few without other risk factors such as high blood pressure or high cholesterol, being obese doesn't raise their risk of cardiovascular trouble.
"Metabolically healthy obese persons do not have the elevated cardiovascular risk of obesity, but represent only a small subset of the total obese population," said lead researcher Dr Andre van Beek, from the University Medical Centre in Groningen. "It's the metabolic risk profile that counts, and not the weight itself."
He was to present the findings at the Endocrine Society's annual meeting in San Diego, US.
For the study, van Beek's group collected data on 1,325 obese people from among 8,356 people who participated in a large Dutch study.
Among the obese people, only 90 (6.8%) were metabolically healthy, the researchers found. That meant they had no history of heart disease, stroke, diabetes or high blood pressure, or high cholesterol or triglycerides. In addition, none of the 90 were taking cholesterol-lowering drugs.
Over more than seven years of follow-up, only one of these people developed cardiovascular disease. As a percentage (1.1%) this was not significantly higher than heart disease seen in metabolically healthy people who were overweight (1.3%) or normal weight (0.6%), van Beek's team found.
Metabolic risk profile
To see whether you are at risk for heart disease, check your metabolic risk profile, van Beek advised. "If this is normal, be reassured that there is no excess cardiovascular risk independent of weight class," he said.
At least one expert is not convinced that obesity itself does not lead to an increased risk for heart disease.
Dr Gregg C. Fonarow, director of the Ahmanson-UCLA Cardiomyopathy Centre at the University of California, US, said that "while this study did not find increased risk associated with obesity if no metabolic abnormalities were present, it is important to note that other studies with longer-term follow-up have shown there is an increased risk of cardiovascular events in these individuals."
"The balance of evidence suggests that, over the long-term, obesity imparts higher cardiovascular risk, even if metabolic abnormalities are not present at baseline," he said.
Shortcomings of study
A researcher specialising in diabetes and metabolic syndrome also thinks the follow-up period in the study is too short to draw firm conclusions about whether certain obese people are protected from heart disease.
Dr Tae-Hwa Chun, an assistant professor of internal medicine at the University of Michigan, said that "clearly we need to know why some overweight and obese individuals are protected from metabolic deterioration and increased cardiovascular risk."
This study suggests that identifying the genetic and molecular mechanism that underlies the deadly link between obesity and cardiovascular risk, which is selectively found in a subset of individuals, is more important than simply measuring body-mass index, Chun said.
"There is a caveat in this study, however, as the cardiovascular event rate is so low in the short follow-up period, the study may not possess enough statistical power to detect a potential difference in cardiovascular risk," he said. - (Steven Reinberg/HealthDay News, June 2010)