MONDAY, Aug. 20, 2012 (HealthDay News) -- People who are obese and suffer from high blood pressure and other problems linked to heart disease and diabetes may also see a faster decline in their mental abilities, according to a new study by French researchers.
Yet even obese people without these physical conditions experienced a faster decline in functions such as memory, the researchers noted. This finding belies the concept of being obese and healthy, they added.
"The prevalence of obesity is rising; 400 million adults were obese in 2005 and this number is expected to rise to over 700 million by 2015," said lead researcher Archana Singh-Manoux, research director of the Center for Research in Epidemiology & Population Health at INSERM, in Paris.
Obesity is known to be bad for health, she said. It is associated with a higher risk of early death and chronic illness.
"Our results add to this list of adverse health effects, showing poorer [mental] outcomes among the obese," Singh-Manoux said.
Having high blood pressure, high cholesterol or high blood sugar, or being on medication to control these conditions, are among the signs of metabolic syndrome. This cluster of symptoms is considered a forerunner for heart disease and diabetes.
For the study, participants with at least two of these signs were considered to have metabolic syndrome.
Participants came from the long-running Whitehall II study, which began in 1985 and follows British civil servants from middle age onward.
For the new findings, researchers followed more than 6,400 people aged 39 to 63 for 10 years. At the start of the study, they recorded patients' risk factors, including weight.
During the follow-up decade, participants also took tests on memory, reasoning and overall mental function at three intervals, according to the report published in the Aug. 21 issue of the journal Neurology.
People with metabolic syndrome who were also obese saw a more rapid decline -- 22.5 percent faster -- in their mental function than those who weren't obese and didn't suffer from the syndrome.
Moreover, those who did not have metabolic syndrome but were obese also saw mental function decline more quickly than participants who were not obese.
Obesity is a known risk factor for many adverse health outcomes, including dementia. It typically is accompanied by metabolic syndrome, Singh-Manoux said. This, however, is not always the case, leading to the concept of so-called "metabolically healthy obesity," she said.
"Some research suggests this type of obesity carries less health risk, but the evidence is far from clear," Singh-Manoux said.
"Our results show this not to be the case for mental function," she said. "Obesity, in those who were metabolically healthy and unhealthy, was associated with poor mental function at the start of the study and greater decline over 10 years."
Dr. Richard Lipton, professor and vice chairman of neurology at Albert Einstein College of Medicine in New York City, said that "this study suggests that taking the steps recommended to prevent heart attack and stroke in midlife, including controlling body weight, high blood pressure, diabetes and lipid profiles, may also have a beneficial effect on cognitive function late in life."
Although more studies are needed, people should heed the advice on how to protect their hearts, Lipton said, which will, in turn, protect their brains as well.
"Maintaining normal body weight while preventing or treating abnormalities in blood pressure, glucose regulation and lipids may provide a therapeutic twofer, protecting the heart and brain," he said.
To learn more about obesity, visit the U.S. National Library of Medicine.