Imagine a pizza slice dripping cheese seductively off of a plate, or envision a thick, rich chocolate bar. Hungry? You're in good company, says Yale University graduate student Ashley Gearhardt. These "hyperpalatable" foods are specifically engineered to spark cravings, triggering brain responses that look surprisingly like the brain's response to alcohol or even hard drugs, according to her research, conducted under the mentorship of Yale obesity researcher Kelly Brownell, PhD, and Arizona State University addiction researcher Will Corbin, PhD.
Unfortunately, people aren't struggling with the nutritious foods they actually need more of, she says. Instead, the food that is "really jacked up" in its reward value is junk food, like french fries, "where you'd benefit if you never had another one," she says.
Gearhardt began wondering whether food can be addictive when, as an undergraduate, she heard Caroline Davis, PhD, a professor at York University and Oxford University, discuss whether eating behaviors might share similarities with addictive behaviors — a line of research being explored by a few researchers via animal models. "I found the idea fabulously interesting, but it was a field that really hadn't evolved yet," says Gearhardt.
So she began studying traditional addiction as a psychology graduate student under Corbin. She found herself again drawn toward food when Brownell gave a guest lecture to her class. Brownell's talk clinched her focus: Instead of studying well-established addictions, Gearhardt would help pioneer the entirely new field of food addiction. It was a gutsy move, but one that has been fruitful. Gearhardt has been first author on 10 published or in press papers over the last two years alone — a remarkable feat for a graduate student, says Brownell.
"Ashley Gearhardt has done groundbreaking work," Brownell says, "and it is being noticed in the scientific world and beyond."
The team's first task was to develop the Yale Food Addiction Scale, first published in the journal Appetite (Vol. 52, No. 2) in 2009. The measure takes the substance-dependence criteria from the revised fourth edition of the Diagnostic and Statistical Manual of Mental Disorders and translates them to reflect eating behaviors associated with foods high in fat, salt and sugar.
The seven-item scale has since been cited in 13 published studies, used in a number of ongoing studies and translated into several languages. "I think the strength of our scale is that it takes the gold standard for diagnosing any other sort of addiction and applies it to eating behavior," she says.
To test the scale, Gearhardt and her colleagues used functional magnetic resonance imaging to examine the brains of 48 women as they viewed images of a chocolate milkshake and again when they sipped a milkshake. When participants who met the criteria for food addiction saw the milkshake pictures, they showed high levels of activation in brain areas associated with craving and motivation, including the caudate and the medial orbitofrontal cortex, according to results published in the April Archives of General Psychiatry. They also found that the addicted women's brains were less active in the lateral orbitofrontal cortex, a region associated with self-control, while they were actually drinking the shake.
"The findings suggest that besides behavioral similarities among people who might be addicted to food and those addicted to other substances, there may be potentially similar biological underpinnings as well," Gearhardt says.
The research also suggests that people with food addictions respond to food cues in much the same way that alcoholics respond to drinking cues. That initial stimulus — a picture of a pizza, a smoky bar — sparks deep-seated cravings in both cases, she says. Also, the dulled restraint-related brain activity that takes place when a food-addicted person drinks a milkshake may parallel what happens with alcoholics who take a sip of alcohol and then can't stop drinking, the findings suggest.
The team was shocked at the strength of the findings, which showed medium to large effect sizes both in food addicts' sighting of cues and in consumption, says Gearhardt. A subsequent trip to the Obesity and Food Addiction Summit in Seattle brought the issue home for her, she says. At the conference, people who described themselves as food addicts shared their struggles. One woman said she often lacked the energy to play or interact with her child because she felt "hung over" from the amount of food she had consumed. A man talked about missing work after a junk-food binge because he felt so sluggish and fatigued.
"Hearing their stories and their frustration in having their experience dismissed by the scientific and clinical community really brought this work to a new level for me," says Gearhardt.
The Big Picture
Gearhardt and her colleagues are expanding their initial findings. In one study, they're examining people's brain activity in response to food ads that feature these uber-engineered consumables. In another, they're collaborating with researchers in the Harvard Nurses' Health Study, where they're using an abbreviated version of their addiction scale to examine associations between obesity and food addiction in a large community sample. They're also planning to study which foods are most addictive, Gearhardt says.
"If we're going to combat the food addiction process, we'd better have strong evidence to show what those foods are," she says.
Combating food addiction, however, can't be done through research alone, Gearhardt and Brownell say. The country needs policy solutions as well, such as taxing potentially addictive food and drink items; restricting the inclusion of these foods in vending machines; or limiting junk-food advertising to children, who otherwise are all too easily sucked into images of gooey, fattening candy bars or cheese-laden pizza slices.
For his part, Brownell is confident that Gearhardt's already groundbreaking work will continue to provide solid evidence to back up the notion that some foods are indeed designed to lure us in.
"Ashley is still technically a grad student," he says, "and she's one of the leading figures in this important and exciting field."
Tori DeAngelis is a writer in Syracuse, N.Y.
Are you a food addict? Try out Gearhardt's diagnostic tool.