"The removal of choice is less threatening if it is done to protect against a situation in which the individual has no real choice anyway, as is the case with addictive substances," said Dr. Ziauddeen. "In short, if there is an addictive agent in some foods, then policy change and legislation can be seen as protective rather than restrictive." This is only possible however, he said, if there is "clear, consistent evidence that there is indeed an addictive substance in food."
And yet, regarding a connection between obesity and food addiction, "the most striking finding is complete inconsistency," said Dr. Fletcher. "I would like to see the same sorts of changes that those supporting food addiction would like, but I do not think that we are going to succeed by using a poorly specified concept with little real evidence to back it up."
Dopamine response not reliable measure
"Food addiction may well exist, [but] even then, it may only explain a tiny fraction of obesity and overeating," according to Dr. Fletcher. "Perhaps the major problem is our general limitations in our often dopaminergically centered views of what constitutes addiction."
A full understanding of the brain’s pathophysiology is still under development, he said. But in addition to classic behavioral manifestations, such as persistent use of a substance, accepted components of addiction include reduced dopamine-receptor density in the ventral striatum and a flip in the neurocircuitry for decision making from the ventral to the dorsal striatum.
Otherwise, he said, conclusive statements about the neurobiology of addiction are suspect. "When we run a functional neuroimaging experiment, we are looking at many different brain regions and, for pretty much all of these, there is a fairly dense ambiguity about what processes they carry out."
In addition, said Dr. Fletcher, although several researchers have tried to replicate one particular study showing that that showed those with severe obesity had reduced raclopride, an indication their dopamine reception was suppressed, the various findings have been inconsistent, thus, said Dr. Fletcher, "there is no proof that there is reduced dopamine in obesity" (Lancet 2001;357:354-7).
As the field of addiction research advances, there will be a shift in the viewpoint that dopamine is the "end all and be all," in part because there will be a deeper understanding of individual variability to different substances that lead to different forms of eating pathologies, he said. "We need to entertain the notion that no single characteristic will define the nature of reward-processing in obesity and that there may be many routes to positive calorie balance."
Longitudinal studies of individual variability to certain foods also could help better determine the impact of certain foods on the brain, he said.
Winners and ‘losers’
"In terms of those who stand to gain from the acceptance of food addiction," said Dr. Fletcher, "At first glance, this would seem to be the people who offer treatments for food addiction and the people who might make some money by suing [processed food] companies."
Yet, for Dr. Gearhardt, if food addiction is proved, and a direct line can be drawn between the food industry’s intentional manipulation of ingredients to profit from this "brain hijacking," Dr. Gearhardt said, "This brings up the question of industry culpability and the ethics of aggressively marketing it to children."
Dr. Gearhardt also believes the possibility of a clinical food addiction diagnosis for those who struggle with pathological eating might "encourage more people ... to receive professional help rather than beat themselves up for not being able to stick to diet after diet on their own."
Conversely, Dr. Ziauddeen noted what while a food addiction diagnosis may offer someone consolation and motivation to seek help, "What if the person is subject to restrictions or treatments based on the diagnosis?" Specifically, he cited ineligibility for bariatric surgery or less clout in the eyes of the court for child custody. "This does not require a stretch of the imagination," he said. "If you have a diagnosis of alcohol dependence, it influences your chances of receiving a liver transplant. If you have a diagnosis of drug or alcohol addiction, it impacts social care decisions made about your children."
Accepting food addiction as real will affect not only those given the diagnosis, but also the so-called "unaffected" public, said Dr. Fletcher. "If food ‘X’ is addictive, to what extent should it be controlled?" He also suggested that health care provision would experience overhaul: "What will be the effect of diverting funding to food addiction treatment from other obesity-related treatments?"