ATLANTA – It’s too soon to disrupt current obesity treatment by declaring food addiction to be a clinical condition, according to Dr. Paul Fletcher.
"If we are to employ [the term] food addiction ... it needs a firm scientific basis," said Dr. Fletcher, who is the Bernard Wolfe Professor of Health Neuroscience in the department of psychiatry at University of Cambridge (England).
Organized medicine took the first step toward recognizing food addiction as a clinical diagnosis with the 2013 inclusion of binge eating disorder (BED) in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). That recognition has the potential to set the stage for an overhaul in delivery and funding of obesity treatment as well as how people with pathologic eating behaviors are viewed.
Obesogenic environment
For some, the answer to obesity and food addiction is to remove unhealthful foods from the environment. And to address "powerful environmental drives to consume them," Dr. Hisham Ziauddeen, a Wellcome Trust Fellow in Translational Medicine and Therapeutics at Cambridge, said in an interview.
Dr. Paul Fletcher
In a separate presentation at a meeting, sponsored by the Obesity Society and the Society for the Study of Ingestive Behavior, Ashley Gearhardt, Ph.D., noted that researchers do not know whether food addiction exists. "The science is emerging." Foods high in fat and sugar, especially when aggressively marketed to children, are the chief culprits of the obesity epidemic, according to Dr. Gearhardt, a clinical psychologist at the University of Michigan, Ann Arbor.
"If scientific evidence identifies that certain foods are also capable of hijacking the brain in an addictive manner, it would likely be a landmark change that would support bold policy approaches that focus on improving the food environment," she has said (Biol. Psychiatry 2013;73:802-3).
Current research in the field is focused on the individual risk factors for compulsive eating, such as impulsivity or reward sensitivity, Dr. Gearhardt said. However, the lack of addictive behaviors associated with "minimally processed foods that are relatively low in sugar and fat, such as apples or chicken breasts," means research now needs to determine if there is something about the food or behavior "that leads to compulsive problematic use," she said in an interview.
"Individual approaches may be helpful in developing clinical interventions but will touch the lives of far fewer people than will policy changes that affect entire populations," she said.
Dr. Gearhardt and her associates sought to link obesity to addictive patterning in the brain through the combined use of functional neuroimaging (fMRI) and scores on the Yale Food Addiction Scale (YFAS), which applies substance-dependence criteria in the DSM-IV-TR as a type of metric for addictive eating behaviors.
The investigators used fMRI maps of participants’ brain activation when they were given food cues of either a tasteless substance or a chocolate milkshake high in fat and sugar. These images were then compared with the participants’ scores from the YFAS. The group was a mixture of both lean and obese women (Arch. Gen. Psychiatry. 2011;68:808-16).
The researchers found that when presented with a chocolate milkshake, those with higher YFAS scores, regardless of body mass index, experienced "significantly greater activation" in brain regions associated with dopaminergic release, including the anterior cingulate cortex. Those with the highest YFAS scores experienced a significant increase in activity of the dorsolateral prefrontal cortex.
‘Elegant experiments’
While fMRI research into the neurobiologic response to food has "generated some very elegant experiments," according to Dr. Fletcher, he is concerned that food addiction proponents have neglected to see these data in a larger context. "The literature is hugely inconsistent, and ignoring this fact may be inconvenient ... but if we continue to do so, it will come back to slap us in the face."
Because neuroimages "are often ambiguous, unless they are constrained by a specific hypothesis, it becomes more like reading tarot cards than interpreting scientific data," he said. "There is a dangerous tendency for people to have a particular perspective and then, no matter what the fMRI data show, to interpret them according to the perspective with which they started out."
And while this free hand with data interpretation happens generally, Dr. Fletcher said he has been "particularly struck" by its occurrence in the food addiction field. "There seem to be very few constraints on interpretation of the regional activation," he said, noting that whether researchers are looking at obesity, binge-eating, or anyone assumed to have a food addition. "Inevitably, [the researchers] find differences in neural activation in such groups but the interpretations of those activations are often post hoc and heavily biased by what the researchers believed in the first place."