Obesitity shrinks brain, makes it older
The study centered on how carrying excess weight might affect the brain's white matter, which facilitates communication between different brain regions.
White matter tissue is known to shrink with age. But the new study found that the amount of white matter in the brain of a 50-year-old overweight/obese person was comparable to that of a 60-year-old lean person.
"Obesity is associated with a host of biological processes that are seen in normal aging," said study author Lisa Ronan, a research associate in the department of psychiatry at the University of Cambridge in England.
"And therefore we hypothesized that obesity may in fact compound the effects of aging that we see in the brain. This is what we found."
Ronan stressed that it's "too early to tell" what this really means. "However, it is possible that being overweight may raise the risk of developing disorders related to neurodegeneration such as Alzheimer's disease or dementia," she said.
Still, the study didn't prove obesity causes premature brain aging. And, Ronan noted that "there were no differences in cognitive ability between overweight and obese people and their lean counterparts."
Ronan and her colleagues focused on nearly 500 men and women between the ages of 20 and 87. All were residents of the Cambridge region and in good mental health.
About half were "lean" (at a body mass index or BMI between 18.5 and 25). Nearly a third were "overweight" (BMI 25 to 30), and about 20 percent were "obese" (BMI over 30). Body mass index is a measure of body fat based on weight in relation to height.
Initial white matter measurements generally revealed that overweight/obese participants had notably reduced white matter volume compared with lean participants.
And an age breakdown revealed that a middle-aged participant who was either overweight or obese had a white matter volume comparable in size to that of a middle-aged lean participant a decade older.
The study authors stressed that the 10-year white matter difference was only seen among those middle-aged and older, not among participants in their 20s or 30s. This, they said, suggests that the brain may become increasingly vulnerable to the impact of excess weight as people grow older.
"At the moment, we really don't know what might be driving the correlation between an increased BMI and lower white matter volume," noted Ronan.
"Indeed, it is not yet clear whether being overweight/obese may cause brain changes, or whether brain changes may in some way cause an increase in adiposity (excess weight)," she added. ■