Underweight and Gastrointestinal Distress – A Bidirectional Relationship?

An Asian cross-sectional study found that underweight was linked to functional dyspepsia (FD), regardless of the presence of anxiety, although anxiety was additionally associated with FD.

The study by Kee Huat Chuah, MD, of the University of Malaysia in Kuala Lumpur, and colleagues, also found no link between high body mass index (BMI) and other functional gastrointestinal disorders (FGIDs). People with FGIDs often have irritable bowel syndrome, functional dyspepsia, or functional constipation. These conditions affect up to 40% of people at any one point in time, two-thirds will have chronic, fluctuating symptoms. The questionnaire-based study recruited 1002 adult individuals with a median age of 32, with 20.7% having FGID according to the Rome III criteria.

Across different FGIDs, including irritable bowel syndrome (IBS) and functional diarrhea and constipation, FD affected more underweight adults (defined as BMI less than 18.5) compared with a non-FGID control group (13.3% vs 3.5%, P=0.002). Multivariate analysis showed that underweight maintained an independent association with FD, at an odds ratio (OR) of 3.648 (95% CI 1.494-8.905, P=0.004).

The results of a large population study from France were consistent with these findings, which also found that being underweight was independently associated with FD in females.  Diarrhoea may also have been associated with central obesity, but there were too few individuals with diarrhoea to draw conclusions, although a large US population study from 2019 showed that obesity was associated with chronic diarrhoea.

A bidirectional association has been observed in eating disorders (often linked with anxiety disorders) with both a low BMI and FD.  Anxiety and/or eating disorders may have caused FD subjects to have a low BMI.

William D Chey, MD, of Michigan Medicine, who was not involved with the research, said the results were interesting and that they could be applicable to the US population since obesity rates are comparable to those in Malaysia.

“But I do agree it’s important to consider whether these observations are cause or effect,” Chey commented. “In other words, FD might cause people to lose weight or thin people might be more prone to developing FD. I do think there’s face validity to these observations. Remember that patients with functional dyspepsia that have meal-related symptoms of fullness and early satiety are unable to eat very much without feeling ill.”

Patients with postprandial distress syndrome often lose weight as a result, Chey continued. “On the other hand, patients with anorexia often have measurable abnormalities in gastric emptying, but that’s not to say all FD patients have eating disorders. My point is that certain non-GI conditions associated with weight loss can also be associated with abnormal GI function.”

The team called for further studies of longitudinal design to explore whether anxiety causes a low BMI in FD or vice versa. Limitations included not being population based, with the cohort being mostly hospital and university staff members. In addition, the data on psychological disorders came from a subgroup of original participants in the study’s second phase; the number of participants with functional diarrhoea was low; the cross-sectional design did not allow for causality; and the questionnaire only asked about dietary habits.

Source: MedPage Today

Journal information: Beh KH, et al “The association of body mass index with functional dyspepsia is independent of psychological morbidity: a cross-sectional study” PloS One 2021; doi: 10.1371/journal.pone.0245511.

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