“Evidence that food addiction is a valid phenotype of obesity”;
Introduction
The purpose of the article by Caroline Davis, Claire Curtis, Robert D. Levitan, Jacqueline C. Carter, Allan S. Kaplan, and James L. Kennedy (Davis, et al.) entitled “Evidence that ‘food addiction’ is a valid phenotype of obesity” was to investigate the legitimacy of “food addiction” in the human condition. It was also the intention to expand the validation of the Yale Food Addiction Scale (YFAS) to identify individuals with addictive tendencies toward food.
In the last few generations, high fructose corn syrup consumption has tripled, from about 4% of our daily caloric intake to 12% of it. According to the authors, fructose has some biochemical properties that, if left unchecked, could have some serious implications for consumers of this variation from glucose. Fructose is chemically almost identical to alcohol since alcohol is the fermented byproduct of fructose, and the addictive properties of alcohol have been common knowledge for years, now. Fructose also acts differently from glucose in a most interesting way. Glucose triggers a feeling of satiation after a given amount of it has been consumed, fructose, however, bypasses this chemical triggering mechanism, so a feeling of satiation is never reached, or is reached after a much greater consumption of food. This occurs because glucose stimulates the release of insulin, which decreases the desire to eat; fructose does not stimulate the release of insulin, thus the delayed or never reached satiation from consumption. The authors also note that sugar intake, on the whole, “cross-sensitizes to drugs of abuse and vice versa.” This means that repeated exposure to administrations of sugar (even in doses below any effective level) results in the progressive amplification of a response to drugs of abuse, and the other way around. For these reasons, the authors felt this study to be an important one to conduct.
In order to show validity for the “food addiction” (FA) construct, the authors focused on the following three factors in their study:
a. Clinical co-morbidities,
b. Psychological risk factors, and
c. The abnormal motivation for the addictive substance.
HYPOTHESES
The authors based their hypotheses on the three aforementioned factors of their study. The hypothesis for the clinical co-morbidities factor was that Binge Eating Disorder (BED), and more severe symptoms of depression and attention deficit/hyperactivity disorder (AD/HD). The authors cited the “strong co-morbid links to drug abuse” of depression and AD/HD, as well as nearly ten years of research indicating correlations between obesity and AD/HD. As for the risk factors of the psychological nature, the authors hypothesized that those with FA would score higher “on a measure of addictive personality traits” and would show more impulsive tendencies. The hypothesis related to the final factor examined was that the food-addicted participants, in comparison to those without FA, would “report a greater hedonic motivation for food”; and, in response to environmental and emotional triggers, overeat even when not hungry.
PARTICIPANTS
Participants in the study included 72 total obese adults—49 of them women, 23 of them men. Participants were recruited through posters at universities, hospitals, and public institutions; and ads in newspapers and Craigslist-type website listings. Requirements to be in the study were verified via “a short telephone interview” and included a fluent proficiency in the English language, residency in North America for five or more years before enrollment in the study, and women were to be pre-menopausal. Exclusions included any diagnosis/es of any of the following conditions: substance abuse, alcoholism, psychotic disorder/s, or any serious physical or medical illness (e.g., cancer, heart disease, paralysis, etc.).
PROCEDURES
MEASURES
In the study, FA was assessed with the Yale Food Addiction Scale (YFAS), which, according to the authors, has operationalized food addiction according to the DSM-IV’s seven symptoms of substance dependence and modified for eating disorders. Four personality measures were used: the Eysenck Personality Questionnaire-Revised (EPQ-R), the Barratt Impulsivity Scale (BIS), a delay discounting task, and a delay of gratification task. Hedonic eating patterns were assessed with the Power of Food Scale; emotional and externally-motivated eating were assessed with the Dutch Eating Behavior Questionnaire (DEBQ) Emotional Eating and External subscales; binge eating was measured with five items from the Binge Eating Questionnaire, sweet-snacking was measured on the subscale (6 items) of the Eating Behaviors Patterns Questionnaire—designed to “measure the frequency and quantity of sugary snacks consumed between normal meals.”
DATA COLLECTION
Participants all gave informed consent on the day of testing and performed an in-person interview to collect demographic information deemed pertinent. Another interview, a structured clinical interview, was conducted to verify eligibility. Participants were instructed to wear “light indoor clothing” and to remove their shoes when height and weight were measured. Participants were then given a packet of 14 questionnaire assessments of clinical, personality, and eating behavior measures to fill out at home and return at a later time.
RESULTS
There were no significant differences in terms of personal/demographic characteristics between food addicts and non-food addicts. Of the total participants, one-quarter of the participants were identified as food addicts. In terms of clinical symptoms, food addicts showed a significantly higher proportion of diagnoses with BED, a higher prevalence of depression, likelihood of childhood ADD, and higher means scores on the CAARS scales Inattentive and Hyperactive and Impulsive. In terms of personality characteristics and in comparison to those where were not diagnosed with FA, food addicts showed poorer performance on delay discounting and delay of gratification tasks, more impulsive traits were reported on the BIS, and scored higher on measures of addictive personality traits. Food addicts also reported more emotionally driven, binge, and hedonic eating patterns as well as greater food cravings and snacking on sweets. Externally-driven eating was slightly higher for food addicts, though not significantly.
In terms of the YFAS, the authors found the results to provide “very good validation for the [Yale Food Addiction Scale] and its ability to identify individuals with addictive tendencies toward food.”
CONCLUSIONS
As a construct, the authors found results to indicate that food addiction “is a classifiable condition with clinical symptomology and a psycho-behavioral profile similar to conventional drug abuse disorders.” In other words, the authors felt that their results supported their hypotheses that those who score high on the Yale Food Addiction Scale would show similar personality traits, clinical co-morbidities, and the compulsive nature of cravings for the preferred substance to those addicted to drugs of abuse. The authors note that the small sample size was a significant limitation to the application of the results of their study. The over double proportion of women to men should be noted as well. Is this due to an increase in prevalence of obesity in women versus men, or just the greater likelihood of women to respond to the recruitments of this study?