Highly processed foods may share traits with drug abuse
The predominance of obesity in the United States continues to increase, with more than 85% of adults projected to be overweight or obese by 2030. Numerous causes contribute to the obesity epidemic. , such as increased energy intake, increased availability and ease of access to foods, larger portion sizes, and decreased physical activity. Although the causes of obesity are multifactorial, one potential contributing factor is the idea certain foods may be capable of triggering an addictive response in some individuals, which may lead to unintended overeating.
Addictive-like eating has been associated with increased impulsivity and emotional reactivity, which are similarly implicated in substance-use disorders. Therefore, “food addiction” may share common behavioral attributes with other addictive disorders.
Although there is little evidence in humans of what foods may be addictive, animal models suggest that highly processed foods are associated with addictive-like eating. Rats with a weakness towards binge eating exhibit addictive-like behavior in response to highly processed foods, such as Oreo Double Stuf cookies or frosting, but not to their typical chow.
Despite highly processed foods generally known to be highly tasty and preferred, it is unknown whether these types of foods can elicit addiction-like responses in humans, nor is it known which specific foods produce these responses, said Ashley Gearhardt, PhD, U-M assistant professor of psychology and corresponding author of this study.
In this new study University of Michigan researchers propose that highly processed foods share pharmacokinetic properties (e.g. concentrated dose, rapid rate of absorption) with drugs of abuse, due to the addition of fat and/or refined carbohydrates and the rapid rate the refined carbohydrates are absorbed into the system, indicated by glycemic load (GL).
In study one 120 undergraduate participants, who were recruited from flyers on campus or through the University of Michigan Introductory Psychology Subject Pool. Participants were aged 18 to 23 years with an average age of 19.27 years, 67.5 percent were female, 72.5 percent were Caucasian 19.2 percent were Asian/Pacific-Islander, five percent were Hispanic, 4.2 percent were African-American, and 2.4 percent were Other. BMI ranged from underweight to obese. Participants completed the Yale Food Addiction Scale followed by a forced-choice task to indicate which foods, out of 35 foods varying in nutritional composition, were most associated with addictive-like eating behaviors.
In study two, 398 participants were recruited using Amazon’s Mechanical Turk (MTurk) worker pool to complete a study about eating behaviors. Participants were aged 18 to 64 years with a mean age of 31.14, 59.4 percent were male, 76.8 percent were Caucasian, 12 percent were Asian or Pacific Islander, 8.9 percent were African-American, 6.5 percent were Hispanic, and 2.8 percent were Other. BMI, as calculated by self-reported of height and weight, ranged from underweight to obese. Using the same 35 foods, but did not include food-priming information, and were presented with instructions for an adapted version of the forced-choice task in Study One. Participants were asked to rate how likely they were to experience problems, as described by the YFAS, with each of the 35 foods on a Likert scale from 1 (not at all problematic) to 7 (extremely problematic). Demographic information (ethnicity, gender, income, and age) and self-reported height and weight were also collected.
In study one the results showed processed foods, higher in fat and glycemic load, were most frequently associated with addictive-like eating behaviors. For example, the top ten foods chosen most frequently during the task were highly processed, with added amounts of fat and refined carbohydrates/sugar (e.g. chocolate, pizza, cake).
In study two the results consistent with study one highly processed foods, or foods with added amounts of fat and/or refined carbohydrates, were most associated with addictive-like eating behaviors. Nine out of the ten foods at the top of the list were highly processed and high in both fat and refined carbohydrates. Soda (not diet) was the exception, which is highly processed and high in refined carbohydrates, but not fat. Processing was a large, positive predictor for whether a food was associated with problematic, addictive-like eating behaviors. BMI and the Yale Food Addiction Scale symptom count were small-to-moderate, positive predictors for this association. In a separate model, fat and glycemic load were large, positive predictors of problematic food ratings. The Yale Food Addiction Scale symptom count was a small, positive predictor of the relationship between glycemic load and food ratings.
Individuals with symptoms of food addiction or with higher body mass indexes reported greater problems with highly processed foods, suggesting some may be particularly sensitive to the possible “rewarding” properties of these foods, said Erica Schulte, a U-M psychology doctoral student and the study’s lead author.
“If properties of some foods are associated with addictive eating for some people, this may impact nutrition guidelines, as well as public policy initiatives such as marketing these foods to children,” Schulte said.
Dr. Nicole Avena, PhD, assistant professor of pharmacology and systems therapeutics at Icahn School of Medicine at Mount Sinai in New York City, and a co-author on the study, explained the significance of the findings.
“This is a first step towards identifying specific foods, and properties of foods, which can trigger this addictive response,” she said. “This could help change the way we approach obesity treatment. It may not be a simple matter of ‘cutting back’ on certain foods, but rather, adopting methods used to curtail smoking, drinking and drug use.”
In conclusion the researchers write “As an important next step in the evaluation of “food addiction,” future studies should also expand on the current findings by measuring biological responses and directly observing eating behaviors associated with highly processed foods in order to examine whether addictive-like mechanisms, such as withdrawal and tolerance, may be present.”
Which Foods May Be Addictive? The Roles of Processing, Fat Content, and Glycemic Load. PLOS ONE, 2015; 10 (2): e0117959 DOI: 10.1371/journal.pone.0117959
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