A glutton for reward (rather than punishment)? A brief psychological overview of excessive and addictive eating

In a previous article in this blog on shopping addictions, it was highlighted that the form of excessive or addictive behaviour someone develops may depend upon gender. As I noted in that article, men are more likely to be addicted to drugs, gambling and sex whereas women are more likely to suffer from ‘mall disorders’ such as eating and shopping. Food is – of course – a primary reward as it is necessary for our survival. However, it is this reward that gives highly palatable food (such as sugar) its addictive potential, leading to excessive eating as an addictive behaviour. Possible reasons behind such excessive eating in today’s society are many, including the increasing availability of food, a more inactive lifestyle, and financial considerations. Furthermore, as a means of mood enhancement, food is highly rewarding, easily available, low-cost and most of all it is legal!

Such justifications demonstrate some degree of explanatory power, contributing to research into the topic of excessive eating as an area of increasing interest. However, no such explanations address the critical question of why certain people seem to overeat, despite repeated efforts not to. The majority of obese cases tend to result from an over-consumption of energy, independent from a lack of physical activity. Therefore it may be people, rather than food, that need to be of focus here.

Prevalence rates for excessive and addictive eating are highly variable. Past year prevalence rates of eating disorders (particularly binge eating disorder, among older teens and adults typically varies between 1 to 2% but much higher figures have been reported in a variety of studies in a number of different countries (between 6% and 15% depending upon the sample). Based on these many studies that included samples of at least 500 participants, Professor Steve Sussman, Nadra Lisha (both at the University of Southern California) and myself estimated a past year prevalence rate of 2% for eating addiction among general population U.S. adults.

Reward sensitivity is a personality construct of Jeffrey Gray’s Reinforcement Sensitivity Theory, and is thought to control approach behaviour, by means of the dopamine reward centre. Individuals that are highly sensitive to reward are more prone to detect signals of reward in their environment (such as food) resulting in approaching these rewards more frequently, along with responding quicker and more strongly. Research demonstrates associations between reward sensitivity and increased food cravings, body weight, binge eating, and a preference for high fat food. Such findings offer a possible explanation for why only some individuals eat excessively when reward, particularly that produced by food, is a process available to all.

An excessive appetite for food has long been linked to emotional eating with research demonstrating that refined food addicts specifically report eating when they feel anxious. For instance, this is demonstrated in the eating habits of overweight Americans, revealing that women tend to binge eat when they feel lonely or depressed, while men overeat in positive social situations. Research dating back to the early 1990s found that women being treated for eating disorders described feeling less anxious as an episode of binge eating went on. Such research suggests that highly anxious people are more likely to turn to food for comfort, leading to excessive eating, yet in turn cause themselves more anxiety when this comfort is unavailable. For instance, this is demonstrated in the eating habits of overweight Americans, revealing that women tend to binge eat when they feel lonely or depressed, while men overeat in positive social situations.

Research has shown that obese people score higher on impulsiveness personality scales. Impulsivity is a tendency to ‘act on the spur of the moment’, often associated with a failure to learn from negative experience, wherein individuals know the appropriate way to behave but fail to act accordingly. Refined food addicts eat for a ‘pick-me-up’, although they are aware that they are not hungry, suggesting a correlation between reward sensitivity and impulsive reactions to such reward cues. Impulsive individuals have a tendency to react to stress and anxiety, with a craving for immediate satisfaction as a form of relief. Although eating may deliver this reward or relief, it may then condition impulsive individuals to react quickly, with this inapt response, to such feelings in the future; such as with feelings of hunger when feeling anxious. This could explain why repeated attempts to restrict food intake and lose weight, so often results in relapse in obese people.

Associations have also been observed between self-esteem and a variety of excessive eating behaviour populations, such as restrained eaters, bulimic patients, and binge eaters. One explanation for this suggests that individuals with low self-esteem have lower expectations for personal performance, resulting in less effort being made to resist challenges and temptations to their diets. This offers another explanation that individuals with low self-esteem depend more on external cues to control eating, such as how food looks, rather than internal cues, such as hunger, indicating reward sensitivity and resulting in dieters with low self-esteem overeating. Here, low self-esteem combined with reward sensitivity and its further correlations to impulsivity and anxiety, seem to demonstrate a destructive model of influence on behaviour, one trait further amplifying the next leading to continuous eating to excess.

In relation to low self-esteem, low social desirability has been seen to correlate significantly with restrained eating in obese people. High social desirability is most commonly associated with a desire for thinness. Therefore, although an association with eating behaviour exists, high social desirability is more likely to correlate with anorexic behaviours as opposed to excessive eating. Low social desirability, combined with low self-esteem as a cause or effect, could contribute to explaining excessive eating in some individuals, which in turn could be reasoned by contributions of all traits previously mentioned.

Finally, Professor Elizabeth Hirschman at Rutgers University has proposed a general model of addictive consumption that interrelates excessive and compulsive consumption behaviour. This model suggests similar characteristics people exhibit, along with common causes, patterns of development, and the similar functions such behaviours serve for individuals. Many of these have been previously associated with excessive eating in particular, further suggesting a general consumption personality principle.

Dr Mark Griffiths, Professor of Gambling Studies, International Gaming Research Unit, Nottingham Trent University, Nottingham, UK

Further reading

Davenport, K., Houston, J. & Griffiths, M.D. (2012). Excessive eating and compulsive buying behaviours in women: An empirical pilot study examining reward sensitivity, anxiety, impulsivity, self-esteem and social desirability. International Journal of Mental Health and Addiction, DOI 10.1007/s11469-011-9332-7.

Davis, C., Levitan, R. D., Smith, M., Tweed, S. & Curtis, C. (2006) Associations among overeating, overweight, and attention deficit/hyperactivity disorder: A structural equation modelling approach. Eating Behaviors, 7, 266–274.

Hirschman, E.C. (1991) Recovering from drug addiction: A phenomenological account. In Sherry, J.F and Sternthal, B (Eds.), Advances in Consumer Research. Association for Consumer Research, 18, 541-549.

Hodgson R.J., Budd R. & Griffiths M. (2001). Compulsive behaviours (Chapter 15). In H. Helmchen, F.A. Henn, H. Lauter & N. Sartorious (Eds) Contemporary Psychiatry. Vol. 3 (Specific Psychiatric Disorders). pp.240-250. London: Springer.

Sussman, S., Lisha, N. & Griffiths, M.D. (2011). Prevalence of the addictions: A problem of the majority or the minority? Evaluation and the Health Professions, 34, 3-56.

Trinko, R., Sears, R. M., Guarnieri, D. J. & DiLeone, R. J. (2007) Neural mechanisms underlying obesity and drug addiction. Physiology & Behavior, 91, 499–505.