The Newsroom, August 24, 2009
Obesity is on a rampage. The World Health Organization pegs the number of those affected at more than 300 million worldwide, with a billion more overweight. With obesity comes an increased risk of cardiovascular disease, Type 2 diabetes and hypertension.
Now there is more discouraging news.
In a study published in the current online edition of the journal Human Brain Mapping, senior author Paul Thompson, a UCLA professor of neurology, lead author Cyrus A. Raji, a medical student at the University of Pittsburgh School of Medicine, and their colleagues compared the brains of elderly people who were obese, overweight and of normal weight to see if they had differences in brain structure — that is, if their brains looked equally healthy.
They found that obese individuals had, on average, 8 percent less brain tissue than people of normal weight, while overweight people had 4 percent less tissue. According to Thompson, who is also a member of UCLA’s Laboratory of Neuro Imaging, this is the first time anyone has established a link between being overweight and having what he describes as “severe brain degeneration.”
“That’s a big loss of tissue, and it depletes your cognitive reserves, putting you at much greater risk of Alzheimer’s and other diseases that attack the brain,” he said. “But you can greatly reduce your risk for Alzheimer’s if you can eat healthily and keep your weight under control.”
For the study, researchers used brain images from an earlier study called the Cardiovascular Health Cognition Study. Scans were selected of 94 elderly people in their 70s who were healthy — not cognitively impaired — five years after the scan was taken. To define the weight categories, they used the body mass index (BMI), the most widely used measurement for obesity. Normal-weight people were defined as having a BMI between 18.5 and 25; overweight people between 25 and 30, and obese people more than 30. The researchers then converted the scans into detailed three-dimensional images using tensor-based morphometry, a neuroimaging method that offers high-resolution mapping of anatomical differences in the brain.
In looking at both the gray matter and white matter of the brain, researchers found that the people defined as obese had lost brain tissue in the frontal and temporal lobes, areas of the brain critical for planning and memory, as well as in the anterior cingulate gyrus (attention and executive functions), hippocampus (long-term memory) and basal ganglia (movement). Overweight people showed brain loss in the basal ganglia, the corona radiata, the white matter comprised of axons, and the parietal lobe (sensory lobe).
“The brains of obese people looked 16 years older than the brains of those who were lean, and in overweight people looked eight years older,” Thompson said.
“It seems that along with increased risk for health problems such as type 2 diabetes and heart disease, obesity is bad for your brain: We have linked it to shrinkage of brain areas that are also targeted by Alzheimer’s,” said the University of Pittsburgh’s Raji. “But that could mean exercising, eating right and keeping weight under control can maintain brain health with aging and potentially lower the risk for Alzheimer’s and other dementias.”
The research was funded by the National Institute on Aging, the National Institute of Biomedical Imaging and Bioengineering, the National Center for Research Resources, and the American Heart Association.
via More obesity blues: Research shows brains of obese people have less tissue | TheNewsroom.org.
]]>It’s not an addiction but it’s similar, and he’s far from alone. Kessler’s research suggests millions share what he calls “conditioned hypereating” — a willpower-sapping drive to eat high-fat, high-sugar foods even when they’re not hungry.
In a book being published next week, the former Food and Drug Administration chief brings to consumers the disturbing conclusion of numerous brain studies: Some people really do have a harder time resisting bad foods. It’s a new way of looking at the obesity epidemic that could help spur fledgling movements to reveal calories on restaurant menus or rein in portion sizes.
“The food industry has figured out what works. They know what drives people to keep on eating,” Kessler tells The Associated Press. “It’s the next great public health campaign, of changing how we view food, and the food industry has to be part of it.”
He calls the culprits foods “layered and loaded” with combinations of fat, sugar and salt — and often so processed that you don’t even have to chew much.
Overeaters must take responsibility, too, and basically retrain their brains to resist the lure, he cautions.
“I have suits in every size,” Kessler writes in “The End of Overeating.” But, “once you know what’s driving your behavior, you can put steps into place” to change it.
At issue is how the brain becomes primed by different stimuli. Neuroscientists increasingly report that fat-and-sugar combinations in particular light up the brain’s dopamine pathway — its pleasure-sensing spot — the same pathway that conditions people to alcohol or drugs.
Where did you experience the yum factor? That’s the cue, sparking the brain to say, “I want that again!” as you drive by a restaurant or plop before the TV.
“You’re not even aware you’ve learned this,” says Dr. Nora Volkow, chief of the National Institute on Drug Abuse and a dopamine authority who has long studied similarities between drug addiction and obesity.
Volkow is a confessed chocoholic who salivates just walking past her laboratory’s vending machine. “You have to fight it and fight it,” she said.
Conditioning isn’t always to blame. Numerous factors, including physical activity, metabolism and hormones, play a role in obesity.
And the food industry points out that increasingly stores and restaurants are giving consumers healthier choices, from allowing substitutions of fruit for french fries to selling packaged foods with less fat and salt.
But Kessler, now at the University of California, San Francisco, gathered colleagues to help build on that science and learn why some people have such a hard time choosing healthier:
_First, the team found that even well-fed rats will work increasingly hard for sips of a vanilla milkshake with the right fat-sugar combo but that adding sugar steadily increases consumption. Many low-fat foods substitute sugar for the removed fat, doing nothing to help dieters eat less, Kessler and University of Washington researchers concluded.
_Then Kessler culled data from a major study on food habits and health. Conditioned hypereaters reported feeling loss of control over food, a lack of satiety, and were preoccupied by food. Some 42 percent of them were obese compared to 18 percent without those behaviors, says Kessler, who estimates that up to 70 million people have some degree of conditioned hypereating.
_Finally, Yale University neuroscientist Dana Small had hypereaters smell chocolate and taste a chocolate milkshake inside a brain-scanning MRI machine. Rather than getting used to the aroma, as is normal, hypereaters found the smell more tantalizing with time. And drinking the milkshake didn’t satisfy. The reward-anticipating region of their brains stayed switched on, so that another brain area couldn’t say, “Enough!”
People who aren’t overweight can be conditioned hypereaters, too, Kessler found — so it’s possible to control.
Take Volkow, the chocolate-loving neuroscientist. She’s lean, and a self-described compulsive exerciser. Physical activity targets the dopamine pathway, too, a healthy distraction.
Smoking didn’t start to drop until society’s view of it as glamorous and sexy started changing, to view the habit as deadly, Kessler notes.
Unhealthy food has changed in the other direction. Foods high in fat, sugar and salt tend to be cheap; they’re widely sold; and advertising links them to good friends and good times, even as social norms changed to make snacking anytime, anywhere acceptable.
Retrain the brain to think, “I’ll hate myself if I eat that,” Kessler advises. Lay down new neural reward circuits by substituting something else you enjoy, like a bike ride or a healthier food.
Make rules to resist temptation: “I’m going to the mall but bypassing the food court.”
And avoid cues for bad eating whenever possible. Always go for the nachos at your friends’ weekend gathering spot? Start fresh at another restaurant.
“I’ve learned to eat things I like but things I can control,” Kessler says. But he knows the old circuitry dies hard: “You stress me enough and I’ll go pick up that bagel.”
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