Emotional? Your Brain On Food
Willpower plays a role in dieting.
But keeping the weight off after you've lost it? This is where our
physiology can get in the way. Research suggests that hormone shifts
that follow weight loss play a role in changing the way our brain
responds to food.
"After you've lost weight, you have an increase in the emotional
response to food," says Columbia University Medical Center researcher
Michael Rosenbaum, who studies the body's response to weight loss. He
says you also see "a decrease in the activity of brain systems that
might be more involved in restraint."
And there's another factor making weight loss maintenance tough, too: a
slower metabolism. When you lose weight, the body adapts to conserve
energy, so it just doesn't need as many calories.
One of the hormones that play a role in controlling appetite in the body
is called leptin. After significant weight loss, leptin levels drop.
This seems to signal to the brain a need to seek more food.
Rosenbaum and his colleague Joy Hirsch, a neuroscientist at Columbia
University Medical Center, designed an experiment to better understand
the relationship between the brain, leptin and weight-loss maintenance.
They recruited overweight volunteers who agreed to a calorie-restricted
diet aimed at shedding 10 percent of body weight. Using fMRI scans, the
researchers looked at how the volunteers' brain responses to seeing food
changed after weight loss.
Still Emotionally Attached
During their study, Hirsch and her colleagues found some interesting
patterns of neural activity in their volunteers after they'd lost
For instance, there was more blood flow to areas of the brain known to
be involved in the emotional control of food intake, such as the
brainstem and parahippocampal gyrus.
But here's the fascinating part: When they restored leptin to these
volunteers by giving them injections of the hormone, the brain response
changed. When they saw food, there was more activity in brain areas
associated with conscious decisions.
"It's a feedback mechanism," says Rexford Ahima of the University of
Pennsylvania. Leptin signals the brain; when there's a deficiency of the
hormone, the areas of the brain associated with reward-seeking become
This evolutionary programming is out of sync with what's healthiest for
our bodies. The signal evolved over thousands of years when food was
scarce. It was the brain's way of telling the body to seek food and
protect fat stores. Many people — particularly those who are prone to
gain weight easily — have retained more genes that program us to seek
As for the role of leptin, researchers say it's clear that leptin is not
an anti-obesity hormone — it won't help you lose weight.
But Ahima says the most recent research suggests that leptin — or drugs
that would stimulate leptin signaling — could potentially facilitate the
maintenance of weight loss. So far, this has only been tested in
My Brain's Response To 'The Food Parade'
Researchers tested subjects, including NPR's Allison Aubrey, by showing
them a mirror image of the real foods displayed above. They compared
their brain response to food with the brain activity when it viewed
mundane household objects.
The researchers invited me to their lab at the Neurological Institute at
Columbia to see exactly how the experiment works. Curious about how my
brain would respond to food, I agreed to an fMRI scan.
As I lay in the scanner, I watched through a mirror as research
assistants passed all kinds of foods — from carrot sticks and apples to
Hershey's Kisses and cookies — through my line of sight.
"Think of it as a food parade," explained Hirsch. After 20 minutes of
watching food, the researchers began analyzing my brain responses.
"You will see a very specific circuit in your brain that's associated
with the appreciation of foods," explained Hirsch.
Hirsch says the patterns in my brain images were similar to those of
test subjects with restored leptin. She pointed to areas in my parietal
and frontal lobes that had activated as I watched the "food parade."
"This is the executive part of the brain," says Hirsch. "You're
responding like somebody in a homeostatic [stable] state." This means
that when I saw the images of food, my brain activated decision-making
areas, and there wasn't nearly as much activity in the emotional,
reward-seeking parts of the brain. Hirsch also pointed out that my brain
showed lots of stimulation in areas related to visual processing.
Courtesy Columbia University Medical Center
Researchers spotted drastic difference in Aubrey's brain activity when
she looked at foods, as compared to mundane objects like a cell phone.
Areas of the brain associated with visual stimulation really lit up.
Of course my brain response could change. The brain images captured just
a snapshot in time. But it was fascinating to see that I didn't have a
very emotional response to food. By comparison, images they'd shown me
of mundane household objects — such as a cell phone — didn't evoke
nearly as much activity in the areas associated with executive function
or visual processing.
Hirsch and Rosenbaum's findings were published in the Journal of
Clinical Investigation. They're now working on follow-up studies to
figure out if people's behavior maps with what they're seeing in brain
"It's a work in progress," says Hirsch. But she thinks this research is
showing that our physiology tends to set the brain in one of two modes:
The "regain" mode, which nudges us, emotionally, to seek food. Or the
"retain" mode, which helps us maintain a steady weight. Researchers are
following up with more studies to see if people's eating behaviors
mirror their brain response to food.