It’s certainly tempting to think of some foods as being addictive. Buttered popcorn and doughnuts with sprinkles come to mind. These highly palatable, sugar- and fat-stuffed goodies are clearly “junk foods,” but does unrestrained splurging on them really a food junkie make?
An Internet search would lead you to believe so—not only that “food addiction” is real, but also in offering ways to recognize signs and symptoms, take self-diagnosis “quizzes”, and going as far as giving advice on treatment of our sugar- and fat-hijacked brains and their dopamine-reward systems.
“When you google ‘food addiction,’ Fox News gives you not one but seven ways to beat it,” said James Hill, professor of pediatrics and medicine at the University of Colorado’s Anschutz Medical Campus, in a symposium on Monday, April 28, in San Diego at Experimental Biology. “The concept of food addiction is becoming widely accepted, but a critical evaluation is needed.”
In a earlier interview with ASN, the session’s co-chair Michael Kelley, Senior Principal Scientist for the Wm. Wrigley Jr. Company, said that the goal of the RIS was to have a comprehensive session that evaluated “where we stand” on the issues such as terminology used, mechanism of action, methodologies, and outcome measures. “Central to the review will be questions of what current technologies tell us, what they are not capable of telling us, and where we should go from there,” he said.
The symposium took place at the American Society for Nutrition (ASN) Scientific Sessions and Annual Meeting. ASN’s Nutrition Translation Research Interest Section (RIS) organized the session in collaboration with ILSI NA.
The evidence for food addiction
Providing some support for the food addiction model are studies in animals, some functional magnetic resonance imaging (fMRI) studies, and studies that have used the Yale Food Addiction Scale that was created through applying the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria.
Calling the food addiction model “conceivable” is neuroscientist Kent Berridge, of University of Michigan, who studies how the brain reacts to sensory pleasures. He does this through a series of animal experiments using drug microinjections and lasers, including comparing facial expressions of (cute!) rats and human babies in response to bitter and sweet.
Using these techniques, Berridge’s lab has been able to map “hedonic hotspots” in the brain, where patterns of firing neurons signal a ‘liking’ response to sensory pleasure such as to that of sweetness. “The brain sees a difference between ‘liking’ and ‘wanting’,” he said. And it’s a major difference. “‘Liking’ for food exists, but the brain system for ‘wanting’ is much larger, more robust, and complex.”
The more intense ‘wanting’ of a reward, or what Berridge calls incentive salience, is of a psychological nature, for example, and doesn’t have to necessarily provide sensory pleasure. This may be because unlike pleasure ‘liking’, reward ‘wanting is driven by dopamine.
Berridge also highlighted the work of Brookhaven National Lab’s Dr. Gene-Jack Wang and colleagues who showed that dopamine reward circuitry in the brains of obese binge eaters and drug addicts had some similarities. For example, obese binge eaters have a higher dopamine release in their brains in response to food cues.
Research neurologist Nicole Avena, of Columbia University’s New York Obesity Research Center, said these food cues are all around us in our modern environment in the form of highly palatable foods rich in sugars and fats that taste good. It’s “hedonic eating” versus eating to gain calories to survive. “People eat because they want to eat, not because they have to eat. They eat because they’re bored or stressed,” she said.
That doesn’t necessarily mean we’re all addicted, but that some foods can lead to addictive-like behaviors.
Providing some support for the food addiction model are studies in sugar-bingeing rats from Avena’s lab. She said that they found that while increases in dopamine tend to fade in response to their regular chow, the opposite happens with exposure to sugar. The dopamine release rises. A similar effect was also seen in response to fat by another lab. “When we give rats sugar, they overeat the sugar. They will also develop a pattern where they consume more and more in a month,” she said.
Those sugar-bingeing rats also work harder to get to cues associated with eating more sugar, even if it means getting shocked with electricity. They are also more likely to consume alcohol and show signs of anxiety withdrawal symptoms, she said.
Although there is little evidence of humans having withdrawal symptoms in response to sugar or fat, Avena said, the work of Yale psychologist Ashley Gearhardt and colleagues have evaluated neural correlates of addiction through fMRI images. In addition, they created the Yale Food Addiction Scale and have used it in studies to identify those with possible food addiction-like disorders.
The evidence against food addiction
Unconvinced of the validity of the Yale Food Addiction Scale, however, was psychiatrist Hisham Ziauddeen, of the University of Cambridge. Reminding that the DSM-IV was designed specifically for abuse of substances such as drugs that lead to tolerance and withdrawal, he said, “The DSM-IV criteria was never set up for a substance that you need.”
Ziauddeen also said that the evidence from the rat-brain studies and brain imaging scans weren’t very useful for obesity. The animal models don’t translate well to humans, for example, and the clinical overlap is unconvincing. By the same logic one could argue that water was addictive because it acted in the same neurons as cocaine.
In addition, the classification for considering which foods would be addictive and not is too “broad and imprecise”. “Consider the problems,” he said. What would be regulated or implemented? Would cheesecake be illegal? Or, how would cheesecake be available from one population but restricted from another?
Neurologist Dr. Miguel Alonso-Alonso, of Harvard University, dug deeper into the problems with using fMRI studies to support the food addiction model. “Money, sex, and art activate the same regions,” he said.
There are also differences in the way food activates the brain versus drugs. There are even differences depending on, say, one peels an apple in a real-life setting versus in an fMRI setting. There’s also a problem of treatment. What would it be? “From diet studies, we already know that abstinence diets or rigid restriction diets are likely to fail,” he said.
What is likely a better strategy, Alonso-Alonso said are interventions targeting “cognitive control” (e.g. physical activity, mindfulness) to promote healthy eating and maintaining a healthy weight.
Closing out the symposium, biostatistician David Allison of University of Alabama offered his thoughts on how to move forward on neurocognition research. He warned against being “blinded” by a new technology like brain imaging that can appear “fascinating and cool” To be valuable and valid, he said, there needs to be meaningful questions, valid designs, proper analyzation of the data, and proper interpretation of results. “If we want to know if X exists, then we have to define what X is,” Allison said. “It’s important to have clear criteria. What is ‘food addiction’? How do we do research well?”
Mostly what we need is “sound thinking,” Allison said. One example of sound thinking about fMRIs and food addiction, he said, is found in an article written by Yale Prevention Research Center’s own Dr. David Katz:
“… a paper by Gearhardt and colleagues in the Archives of General Psychiatry shows that those individuals scoring higher on a scale for “food addiction” have more intense responses in the reward circuitry of the brain, revealed using functional MRI scans, than counterparts scoring lower.
The media attention this study has generated would suggest that it delivers an epiphany. But I think the case is just as strong that it delivers a tautology: those who report receiving a stronger, more irresistible reward message from their brain in response to food have a stronger, more irresistible reward response in their brain in response to food.
With or without brain scans, we knew that food affects the brain.”