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Every morning, Nora Volkow walks past a vending machine on her way to her office. She barely notices it. One day, however, she’s hungry, so she stops and peers in. A chocolate bar grabs her eye. She inserts her money, takes the chocolate, munches, and moves on. The next day, Volkow walks to her office as usual, but this time as she rounds the corner, she has a sudden, intense craving for chocolate. She hadn’t thought about it since her last bite the day before. She isn’t hungry. “But my brain responded in this automatic way,” she explains in her melodic Spanish accent as she sits in her office at the National Institute on Drug Abuse (NIDA), where she serves as director. Because the chocolate had given her so much enjoyment, just the sight of the machine made her want to eat more.
Volkow, a lithe woman with short blonde curls, provides example after example of instances in which she has succumbed to the food’s lure. Chocolate-covered raisins. Godiva at a bookstore. Chocolate-chip cookies. The woman really, really likes chocolate.
But is she an addict? People talk about being “addicted to sugar,” “addicted to potato chips” and, probably most commonly, “addicted to chocolate.” Volkow has been attempting to figure out whether we truly can be addicted to food by peering into people’s minds with high-tech scanners. She has already shown that obese people’s brains look similar to the brains of those addicted to drugs. She’s finding that food, especially the highly palatable fatty, sugary kinds that pack the inner aisles of American supermarkets, fast-food joints and, yes, vending machines, can enslave anyone and change their behaviors.
The more she can understand how “rewarding” substances, like drugs and yummy foods, can activate parts of our brains associated with addiction, the more she can help us learn how to take back control of our actions—or never lose our free will in the first place.
The Makings of a Pioneer
If you were to imagine a person whose pedigree and character destines her for a key leadership role, an NIH director, say, you might picture someone quite like Nora Volkow. Volkow’s great-grandfather was Leon Trotsky, the famous Russian revolutionary who defied Stalin, only to later be murdered in exile in Volkow’s childhood home in Mexico City. Her mother, a Spanish fashion designer, died several years ago, and her father is a chemist who still lives in Mexico. Nora Volkow herself graduated first in her class at the National University of Mexico medical school and received the Premio Robins award for best medical student of her generation. She speaks four languages fluently. She runs seven miles before work every day. She works an average of 80 hours every week.
Yet for the sake of science, she perpetually brings up her own weaknesses. Like chocolate. Which we keep coming back to.
“The other day someone gave me chocolate-covered raisins,” she says, swinging her ID chain with both hands, a twinkle in her eye. “They gave me two boxes, so I say, OK, I’ll eat half a box. Well, I ate one-and-a-half boxes!” This sort of compulsive eating, she says, is one reason that obesity has become an epidemic. Many people blame obese people for their condition, saying they simply eat too much. But it’s not that obese people lack willpower, says Volkow; there is something physical happening in their brains that prevents them from stopping. “Obesity is highly, horrifically stigmatized,” says Volkow. “It erodes your self-esteem, it interferes with social interactions, it affects your mobility. And yet so often people cannot stop it.”
The Dopamine Made Me Do It
Volkow’s interest in the chemistry and mechanisms of the brain began in Mexico City in 1981. She had just graduated from medical school and read an article in Scientific American about exciting new clinical applications of a technology called positron emission tomography (PET). PET allows scientists to see a three-dimensional image of the brain as it thinks, feels and works (previously, scientists could not watch the brain in action very well). Volkow was awestruck, and applied for a psychiatric residency at New York University to have a chance to work with nearby PET pioneers at the Department of Energy’s Brookhaven National Laboratory on Long Island.
She was particularly interested in the brains of people who lose the ability to control their actions rationally; people who, in essence, lose free will. At first, she studied schizophrenics. By the late 1980s, she started looking at the brains of alcoholics and drug addicts as well. She soon saw that the addicted brains looked decidedly different from brains of people without drug or alcohol addictions.
The most marked difference was in the dopamine cells of the reward circuit, a group of brain cells that communicate using the chemical dopamine. The circuit connects several regions in the brain involved in the feeling of reward, which has evolved to motivate us to do more of the things that make us feel good and are important for survival, like eating, having sex and taking care of children. Drugs like cocaine and amphetamines highjack this circuit, causing a flood of dopamine into the area between brain cells where messages are transmitted. And this dopamine surge produces a high. Take the drugs often enough and dopamine receptors can decrease in number or become less sensitive to dopamine. When this happens, a person needs more and more of the drug to get the same effect (this is called tolerance).
As a psychiatrist, Volkow noted a similarity between drug abusers and compulsive overeaters: they both seemed to lose their rational ability to control their behaviors (around drugs and food, respectively). She wanted to know how to intervene to help those who couldn’t stop themselves. She knew that antipsychotic drugs, which block the reward-registering dopamine system, often make people eat and gain weight (as a side effect), while drugs that increase dopamine in the brain cause weight loss. In 2001, Volkow and her colleagues began exploring whether dopamine played a key role in overeating and obesity in people not on drugs.
To find out, Volkow and her crew gave a radioactive chemical that binds to dopamine receptors to 20 people—10 obese, 10 normal weight—and then scanned their brains using PET, to see whether there were any associations between their dopamine systems and their body weights.
Turns out, there were. The obese people had significantly fewer dopamine receptors in a part of the brain called the striatum. Volkow and her team surmised that with fewer receptors, the people who were obese had to eat far more food than a normal-weight person to experience the same high.
Liking and Wanting
In 2002, Volkow published a study that investigated the link between dopamine and “wanting.” When people were presented with—but not allowed to eat—warm, tasty plates of their favorite food, dopamine increased in the striatum area of their brains. The subjects said they were hungry and desired the food. This is the “wanting,” or craving; it is not the pleasure (i.e., “liking”) they likely would have experienced if they had been allowed to consume it. The people’s responses in this study were quite similar to the experiences of drug abusers watching a video showing people using cocaine: the abusers experience a dopamine surge through the parts of the brain involved in habit.
In other words, really liking chocolate or potato chips, the pleasure that occurs when your reward systems fire, isn’t the whole story of dopamine and addiction. An intense want—the desire to eat, to do everything you can to get your hands on a food and put it into your mouth—is equally important. You taste creamy milk chocolate or a salty French fry. You really, really like it. So much so that you’re conditioned to the setting in which you ate the yummy food and the next time you’re in that environment, a shot of dopamine squirts into your brain and you want that food. You crave it. You’re motivated to eat it—and to keep eating it.
This idea is central to the obesity epidemic. “There is a certain reinforcement, almost like an arousal of wanting more,” says Volkow. “A person eats a gallon of ice cream. He is not even realizing the taste of the food anymore, he’s not enjoying the pleasure of the palatability and experience; it has become automatic. The drive to have more and more [fueled by dopamine] is what maintains that behavior, independent at that point of the pleasurable response that you get.
“It’s almost like they become a robot.”
You’ve Been Conditioned
No one would become a food-devouring robot, however, if they lived in a desert or on the moon or in the year 1850, according to David Kessler, M.D., former FDA commissioner and author of The End of Overeating (Rodale, 2009). We eat, he says, because we have constant, crippling access to rich, delicious foods packed with fat and sugars, both of which activate our dopamine systems. And those conditioned cues are everywhere—commercials, fast-food restaurants that we pass on our commutes, grocery stores. Kessler postulates that fat and sugar, plus salt, have triggered mass overconsumption in the United States.
“We took fat, sugar and salt and put it on every corner, made it available 24/7, made it socially acceptable to eat anytime. We’re living in a food carnival,” he says.
Volkow’s Bethesda offices are a perfect microcosm of this American food environment: Within one-third of a mile, a visitor can find a frozen yogurt place, a greasy-spoon diner, a Mexican restaurant and at least 10 other eateries. On the first floor of the NIDA offices is a cafeteria with a hot buffet and snacks. Vending machines, like the one Volkow has a hard time resisting, live on the office floors themselves. Bowls of candy lurk on desktops and in drawers. The scent of microwave popcorn pervades the office air.
The continual need to say “NO!” to these tempting foods requires the strongest will, and some people’s wiring seems to be working against them. In a 2008 study, Volkow found that having fewer dopamine receptors (as obese people do) was associated with less activity in parts of the brain responsible for self-control. In other words, these people not only have to eat more to achieve the same “reward,” they also have a harder time stopping themselves from eating once they start. Drug addicts similarly have fewer dopamine receptors, also associated with less activity in the self-control parts of the brain. In the brain of a compulsive, “addicted” eater, inhibition is like a picket fence trying to hold back an avalanche of reward and conditioning.
“Joanne,” 39, from San Francisco, a member of Food Addicts in Recovery Anonymous, agrees, and says that sugar and flour are her drugs. Since she was a teenager, Joanne would compulsively eat for hours at a time; in high school she learned how to make herself sick, which “led to 15 years of insanity,” she says. “There was something in my brain that would light up, and it would turn into this massive craving that I could not control.”
Joanne’s food addiction manifested as bulimia, but others in the group became obese. When she wasn’t purging, she was “white-knuckling it” through the day. “If there was food somewhere in the vicinity, the constant conversation in my head was, ‘Should I eat that? No, don’t eat that.’ Back and forth, over and over, while trying to maintain a conversation, which was almost fruitless because I wasn’t really listening, I was focused on the food.” Studies have estimated that about 10 percent of the population is addicted to food like this, and many more of us probably fall elsewhere on the food-addiction spectrum.
“Everyone understands how critical taste is [to overeating], but what Nora has shown is the role not just of taste, but of the brain and brain circuits,” says Kessler. “We now know that the learning, memory, habit and motivational circuits of the brain are what drive eating, and Nora deserves a lot of credit for pulling back the curtain and showing us what’s really at the core of this [obesity] epidemic.”
Breaking the Cycle
But even though we are inundated with hyper-palatable food, not everyone becomes an addict. “At least 50 percent of that vulnerability is related to genetics,” Volkow says. And your ability to put on the brakes is a crucial factor. “Some people are [naturally] much better at controlling their desires than others.” After genetics, Volkow says the rest is environment—if you only have access to high-calorie, cheap junk foods, that’s all you can eat.
Not everyone in the field agrees that people can be addicted to food and they object to the excuse it provides. “Interest in obesity as a brain disease should not detract from a public health focus on the ‘toxic food environment’ that is arguably responsible for the obesity epidemic,” writes psychologist Terry Wilson, Ph.D., of Rutgers University in a 2010 paper. But those who study food addiction say it does bear striking similarity to drug and alcohol addition: Ashley Gearhardt, Kelly Brownell and William Corbin at Yale have created the Yale Food Addiction Scale to determine whether a person is truly addicted to food. They adapted it from the scale for substance dependence in the DSM-IV (the “Bible” of psychiatry), and it includes criteria like whether the subject has been unsuccessful in trying to quit, whether he or she spends a lot of time trying to obtain the food, whether he or she has given up other recreational activities for the food, whether there are adverse consequences of eating the food, whether the subject becomes tolerant to the food and whether they have withdrawal symptoms. When they surveyed 233 people, these three leading researchers found that 11.6 percent of them could be diagnosed with food dependence (consuming large amounts of food despite significant issues—obesity, health problems—associated with it and the desire to stop, as well as withdrawal or tolerance). The scale could be useful in determining treatment for addicts versus those who simply experience the occasional craving.
Back in her office, surrounded by sculptures and paintings, some from her own hand (yes, she’s an artist too!), Volkow talks about how addiction steals our free will and makes us a slave to the salient substance. So is Nora Volkow a chocolate addict? “No, I’m not. We use the word way too much.” The distinction, she says, is when eating the food impairs your life, when you lose control, like when a person consistently eats so much they only eat in private out of embarrassment and spend much of their time thinking about food. “Most people [who] take drugs are not addicted to drugs, like most people who eat chocolate, even if they eat more than they should, are not addicted to chocolate.
“I may have that vulnerability, perhaps, for compulsiveness, but I am lucky enough to also have the control that leads me to plan ahead and say, I’m not going to do these things.” In other words, you can extend a hand from a present moment of strength to a future instance of weakness and wrestle your free will back from the dopamine master within.
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