Among the metabolically unhealthy participants, the non-obese had high levels of hypertension and inflammation - comparable to those in the unhealthy obese group.
The metabolically unhealthy obese also had a 72 percent higher risk of dying from non-heart-related causes than those in good health.
That was after taking into account study participants’ age, sex, smoking, physical activity and socioeconomic status.
Researchers found the results to be largely unchanged when they used waist circumference to define obesity instead of BMI.
‘THINK MORE BROADLY’
Hamer and his colleague note in their report that a strength of their study was having a large study population. But because the researchers only measured participants’ metabolic risk factors at the beginning of the study, it’s possible that some of the metabolically healthy obese went on to develop unhealthy readings.
The study shows the need “to think more broadly about obesity” rather than to focus on body weight alone, said Dr. Cora Lewis, a professor of preventive medicine and an epidemiologist at the University of Alabama, Birmingham, who was not involved in the research.
“If you are obese and you struggle with weight, but your (metabolic) risk factors are fine, that may not be such a bad place to be,” Lewis told Reuters Health - adding that only “a minority of people” fit the description of “metabolically-healthy obese.”
Equally important, the study shows that people may be at increased metabolic risk no matter what they weigh, she noted.
Excess body fat may be carried not only under the skin, but also inside the abdomen, heart, liver and muscles - making it hard to tell - she added.
“BMI doesn’t always tell you everything. If you are non-obese, but you have High cholesterol or hypertension, you have some work to do,” Lewis said.
SOURCE: The Journal of Clinical Endocrinology & Metabolism, online April 16, 2012.
Metabolically Healthy Obesity and Risk of All-Cause and Cardiovascular Disease Mortality
Main Outcome Measure: Study members were followed up, on average, more than 7.0 ± 3.0 yr for cause-specific mortality. Cox proportional hazards models were used to examine the association of metabolic health/obesity categories with mortality.
Results: There were 604 CVD and 1868 all-cause deaths, respectively. Compared with the metabolically healthy nonobese participants, their obese counterparts were not at elevated risk of CVD [hazard ratio (HR) 1.26, 95% confidence interval (CI) 0.74–2.13], although both nonobese (HR 1.59, 95% CI 1.30–1.94) and obese (HR 1.64, 95% CI 1.17–2.30) participants with two or more metabolic abnormalities were at elevated risk. Metabolically unhealthy obese participants were at elevated risk of all-cause mortality compared with their metabolically healthy obese counterparts (HR 1.72, 95% CI 1.23–2.41).
Conclusion: Metabolically healthy obese participants were not at increased risk of CVD and all-cause mortality over 7 yr.
Mark Hamer and Emmanuel Stamatakis
Department of Epidemiology and Public Health, University College London, London WC1E 6BT, United Kingdom