Eating disorder patients commonly complain of gastrointestinal (GI) symptoms including bloating, abdominal pain, and constipation. This is, of course, not surprising. After all, disordered eating behaviours such as self-induced vomiting, laxative abuse, and restriction are bound to have negative effects on the digestive system.
But just how common are GI complaints and functional gastrointestinal disorders (FGIDs) like irritable bowel syndrome among ED patients? And is there more to the relationship than simply ED behaviours causing GI disturbances? Luckily, a growing number of research studies are beginning to shed some light on these questions.
In a study published in 2010, Catherine Boyd and colleagues examined the prevalence of FGIDs among ED patients admitted to a hospital Eating Disorders Unit. They found that out of the respondents (73 in total), 97% had at least one FGID (as evaluated using the Rome II questionnaire). More specifically, on admission, 73% of the participants had esophageal disorders, 32% gastroduodenal disorders, 81% had bowel disorders, and 33% experienced anorectal disorders. At 12-month follow-up, the numbers decreased to 34%, 18%, 66%, and 18%, respectively.
Overall, despite significant improvements in weight, psychopathology, and disordered eating behaviours, 77% of participants had FGIDs at follow-up:
Neither change in BMI nor change in ED behaviors (self-induced vomiting, laxative use, and objective binge eating), and psychological variables (anxiety, depression, and somatization) had a significant interaction with change in individual FGIDs or in FGID regional categories from admission to 12-month follow-up.
In 2011, Dejong et al. published a study investigating the prevalence of irritable bowel disease in outpatients with bulimia nervosa. Out of 64 participants, 44 (68.8%) had IBS. This is compared to around 10-15% in the general population (in the US) (Saito et al., 2002).
That same year, Abraham and Kellow (2011) published a study looking at how FGIDs affect the quality of life among eating disorder patients. The prevalence of FGIDs was 93% in their sample. Interestingly, they found that only IBS, but not other FGIDs, correlated strongly with quality of life scores.
A couple of years prior to these studies, Perkins et al. (2005) examined the temporal relationship between one FGID in particular, IBS, and eating disorders. That is, in addition to determining the prevalence of IBS, they were interested in finding out what came first: the ED or the IBS. They were also interested in identifying any predictors of IBS symptoms among ED sufferers.
Perkins et al. hypothesized that the relationship between IBS and EDs might be more complex than meets the eye in part because
it is has been noticed that there are a number of shared demographic and clinical features between populations with EDs and IBS. Women are overly represented in IBS  and ED populations . In addition, these two conditions have a high prevalence of physical and sexual abuse . Finally, the individuals with these conditions tend to have personality characteristics of perfectionism, negative self evaluation, self-blame and feelings of ineffectiveness [16–20].
Out of 225 respondents, 64.4% had met the criteria for IBS (using the Manning criteria), although only 24.8% had been given a formal diagnosis of IBS. Out of the 89 participants who reported both the age of ED and IBS onset, 87.6% had an onset of their ED prior to IBS symptoms, 6.7% had onset of IBS prior to ED, and 5.6% had onset of EDs and IBS the same time (See figure below).
The bigger (longer?) the bar, the greater the difference (in years) between the onset of IBS and ED.
Note the difference in age of ED onset between those who developed IBS first and those who developed the ED first:
The group developing IBS after the onset of their ED had the typical teenage onset of their ED (mean age 15.8 years) and a lengthy time period between the onset of the ED and the IBS (mean 10.4 years). In contrast, the small group that developed IBS first had a late onset of the ED (mean 25.5 years).
Out of those reporting current IBS symptoms, 63% had a current ED.
What about predictors of IBS symptoms? Perkins et al. found that inappropriate laxative use was significantly correlated with severity of ED symptoms and the number of IBS symptoms. Neither ED duration nor lowest BMI predicted the number of IBS symptoms.
The high prevalence of IBS (and other FGIDs) among patients who have (at least to some extent) recovered from an eating disorder ED populations is interesting. Perkins et al. suggest that perhaps “hyper-vigilance to internal sensations” has a part to play in this.
Just as FGIDs are overrepresented in ED populations, EDs are overrepresented in FGID populations: In a study of 127 patients seeking treatment for an FGID, 15.7% were found to have a history of an ED (Porcelli et al., 1998).
Taken together . . . , our findings suggest that EDs may be predictive of the later development of IBS, irrespective of the persistence of the ED symptoms, but that where there are current EDs, the severity of these correlates with the number of IBS symptoms.
While disordered eating behaviours and other ED symptoms clearly play a role in GI disturbances, it is possible that other factors, such as chronic stress and personality traits, may play a role in causing and/or maintaining EDs and FGIDs:
There seems to be considerable overlap between the personality and early developmental factors cited as increasing the vulnerability to both types of disorders, such as anxious-avoidant personality type or childhood trauma [14,35]. Moreover, recent models of IBS  and of AN , which have tried to integrate findings from psychological and neurobiological research, have highlighted the pivotal role of chronic stress in the origins and maintenance of both disorders, with a combination of central and peripheral mechanisms working in tandem.
All of this is quite interesting and I look forward to future research exploring the relationship between GI symptoms and EDs. (Or perhaps it is already out there and I just haven’t looked hard enough? This is very possible.)
Importantly, a lot of these studies relied on self-reported questionnaires and potentially biased samples, so caution is warranted when interpreting these results (and extrapolating to other populations).
Finally, although it is a bit out-of-date now, Zipfel et al.’s 2006 review of gastrointestinal disturbances in eating disorders is quite good. I couldn’t find a pdf online, so drop me a line if you are interested.
Abraham, S., & Kellow, J. (2011). Exploring eating disorder quality of life and functional gastrointestinal disorders among eating disorder patients. Journal of Psychosomatic Research, 70 (4), 372-7 PMID: 21414458
Boyd, C., Abraham, S., & Kellow, J. (2010). Appearance and disappearance of functional gastrointestinal disorders in patients with eating disorders. Neurogastroenterology and Motility, 22 (12), 1279-83 PMID: 20718945
Dejong, H., Perkins, S., Grover, M., & Schmidt, U. (2011). The prevalence of irritable bowel syndrome in outpatients with bulimia nervosa. International Journal of Eating Disorders, 44 (7), 661-4 PMID: 21997430
Perkins, S.J., Keville, S., Schmidt, U., & Chalder, T. (2005). Eating disorders and irritable bowel syndrome: is there a link? Journal of Psychosomatic Research, 59, 57-64 DOI: 10.1016/j.jpsychores.2004.04.375