[For some time,
scientists have known that many overweight people’s brains operate differently
than the brains of thinner people when they look at images related to eating. In previous neurological studies,
when heavier volunteers viewed pictures of food or food preparation, they
typically developed increased activity in portions of the brain involved in
reward processing, or an urge to like things, including in an area called the
putamen. At the same time, their brains showed relatively blunted activity in
areas that are thought to induce satiety, or the ability to know when you are
full. These changes generally are reversed in the brains of thinner people
shown the same images.]
 |
| David Madison/Getty Images |
Overweight women’s brains respond differently to images of exercise than
do the brains of leaner women, a sophisticated new neurological study finds,
suggesting that our attitudes toward physical activity may be more influenced
by our body size than has previously been understood.
For the study, which was published
last month in The International Journal of Obesity, scientists affiliated with
the Key Laboratory of Cognition and Personality at Southwest University in
Chongqing, China, recruited 13 healthy, young, normal-weight women and 13 who
were overweight or obese.
The scientists asked
their volunteers to complete two questionnaires, one of which probed the extent
to which they considered exercise desirable; would they agree, for instance,
that, “if I were to be healthy and active, it would help me make friends”? The
other set of questions examined whether they expected exercise to be
unpleasant; if they were to be physically active on most days, for example,
would they expect to wind up feeling sore, or maybe even embarrassed by
exercising in public?
The researchers next
had each woman lie inside a functional magnetic resonance imaging machine,
which scans blood flow to specific areas of the brain, indicating areas of
increased activity. Then they started a slide show.
For some time,
scientists have known that many overweight people’s brains operate differently
than the brains of thinner people when they look at images related to eating. In previous neurological studies,
when heavier volunteers viewed pictures of food or food preparation, they
typically developed increased activity in portions of the brain involved in
reward processing, or an urge to like things, including in an area called the
putamen. At the same time, their brains showed relatively blunted activity in
areas that are thought to induce satiety, or the ability to know when you are
full. These changes generally are reversed in the brains of thinner people
shown the same images.
But no brain-scanning
studies had examined whether being heavy might also affect people’s brain
responses — and presumably their attitudes — toward physical activity.
So, to address that
gap, the researchers now flashed a series of photographs before their prone
volunteers. Ninety of the images showed people being joyously active by
running, dancing, leaping, playing tennis and such. The women were asked to
vividly imagine themselves performing the same actions, using hand gestures and
limited bodily contortions, to the extent possible within the confines of the
scanner.
Ninety additional
images featured relaxed, sedentary behaviors, including stretching out on a
sofa and sitting in a desk chair. Again, the women were directed to imagine
themselves similarly lounging. The various images of activity and quiet were
interspersed with photographs of landscapes.
While the women viewed
the pictures, the functional M.R.I. machine monitored their brain activity.
The resulting readouts
revealed that overweight women’s brains were put off by exercise. Shown images
of people being active, these women developed little activation in the putamen
region of the brain, suggesting that they did not enjoy what they were seeing.
At the same time, a portion of the brain related to dealing with negative
emotions lit up far more when they viewed images of moving than of sitting.
Emotionally, the brain scans suggested, they anticipated disliking physical
activity much more than they expected to disdain sitting.
Leaner women’s brain
activity, by and large, was the opposite, with the putamen lighting up when
they watched others work out and envisaged doing the same themselves.
Such data might at
first seem discouraging, underscoring the possibility that being obese or
overweight is self-reinforcing, although it is impossible to know from this
study whether a dislike of exercise contributed to or resulted from weight
gain.
A final and unexpected
finding from the study provides a basis for hope, though. The scans also showed
that when overweight volunteers viewed images of exercise, a portion of their
brain related to movement memory remained stubbornly silent. Their bodies were
unfamiliar with how to be active, which might have contributed, the study’s
authors speculate, to the women’s negative emotional response to activity. They
didn’t know how to exercise and anticipated not enjoying trying to learn.
Interestingly, these
women had also said at the study’s start, when answering the questionnaires,
that they expected exercise to end in embarrassment (while also believing that
if only they could exercise, they would be more popular).
The practical
takeaways of the findings are obvious and almost poignant.
“Encourage people to
pursue physical activities and exercise that they actually find pleasurable and
might enjoy,” said Todd Jackson, a professor of exercise science at Southwest
University, who led the study. Hire a kind, nonjudgmental coach or personal
trainer to lead you through a manageable exercise routine.
And if you continue to
find yourself drawn to the couch instead of the gym, use that inclination
strategically “as an incentive or reward for increasing exercise,” Dr. Jackson
said. Swim for 45 minutes and then allow yourself to surf the Internet, for
instance, he suggests. Don’t fight your brain’s unenthusiastic attitude toward
exercise, he said. Embrace it.
