America's obesity epidemic is prompting psychiatric researchers to focus
more attention on possible interplays between the psyche and being
For example, anxiety, depression, binge eating, and night-eating syndrome
have been linked with obesity. There is also growing evidence that obesity is
related to Alzheimer's disease.
And now a new inquiry has linked obesity with defective executive function.
The investigation, which was headed by John Gunstad, Ph.D., an assistant
professor of psychology at Kent State University, is in press with
The study included 408 subjects aged 20 to 82. each had been screened to
make sure that he or she was free of medical conditions that had the potential
to influence cognitive performance, such as traumatic brain injury,
neurological disorder, high blood pressure, cardiac disease, thyroid disease,
or sleep apnea.
Gunstad and his colleagues gave the subjects various cognitive tests. The
researchers then looked to see whether there were any links between subjects'
performances on the cognitive tests and their body mass index.
A statistically significant link was found between subjects' performances
on all of the cognitive tests and their body mass index—in other words,
body mass index was inversely related to performance on all cognitive tests.
Yet, after taking age, gender, IQ, years of education, and other possibly
confounding factors into consideration, only impaired executive function
significantly differentiated overweight or obese subjects from those of normal
"I think it's a really interesting and novel study of a potentially
important phenomenon," Michael Devlin, M.D., an associate professor of
clinical psychiatry at Columbia University and a binge-eating investigator,
told Psychiatric News. "Although the link between
overweight/obesity and impaired executive function is relatively weak, it's
there, as evidenced by this and other studies.... What is much less clear is
the mechanism and... even the directionality of the link."
Gunstad and his colleagues concurred. As they pointed out in their paper,
it is possible that obesity causes impaired executive function since many of
the pathophysiological changes associated with obesity—for example,
vascular changes, impaired insulin regulation, reduced cardiovascular
fitness—could negatively impact executive function. But, they added, it
is also possible that persons with a defective executive function are more
likely to become overweight or obese since many aspects of executive
function—for instance, impulse control, self-monitoring, goal-directed
behavior—seem to bear directly on the ability to maintain weight.
A similar question pertains to links that have been made between obesity
and various psychological disorders. For example, does obesity lead to
depression, or does depression lead to obesity? The only psychological
disorder that has been demonstrated to cause obesity, not result from it, is
the night-eating syndrome (Psychiatric News, September 16, 2005).
"Additional work is needed to determine the directionality of the
relationship between elevated body mass index and executive function,"
Gunstad and his team concluded in their report, "particularly
prospective studies assessing cognitive performance before and after
significant weight loss."
In fact, Gunstad told Psychiatric News, "We are about to
start [such] a longitudinal project to look at cognitive function in persons
who undergo bariatric surgery. Patients undergoing those procedures lose a
large amount of weight in a relatively short period of time.... This project
is being conducted with researchers at Columbia, including Mike Devlin... and
at the Neuropsychiatric Research Institute in Fargo, N.D."
This exploration, Gunstad continued, should not only help answer the
question of whether obesity impairs executive function or vice versa, but may
well have some practical value.
For instance, "It is possible that persons with deficits in executive
functioning... have more difficulty following recommendations from health
professionals and aren't as successful at losing weight. If this is the case,
neuropsychological screening of patients might identify those likely to have
such problems, and weight-loss interventions could be modified to improve the
likelihood of success."
Moreover, "understanding the possible relationship between cognitive
function and weight loss might be important in working with older adults who
are trying to lose weight. Even healthy older adults show decline in cognitive
function, and it is possible that these changes might make it more difficult
for some to follow the prescribed intervention.... With the growing number of
older adults and the rising prevalence of obesity, weight-loss programs may
need to be tailored for older adults to accommodate these concerns."
This study required no funding. All data were obtained from the Brain
Resource International Database at<www.brainnet.org.au>.
An abstract of "Elevated Body Mass Index Is Associated With
Executive Dys-function in Otherwise Healthy Adults" can be accessed at<www.sciencedirect.com>
by clicking on "Browse A-Z of journals," then "C,"
then "Comprehensive Psychiatry." ▪