Teasing out motivations for vegan and vegetarian diets and their relationship to disordered eating

In her 2022 3MT presentation, Ms Courtney McLean explains

her research into measures of eating disorder for the dietary
choice of veganism and vegetarianism. See video (2:49 mins)

It has long been thought that vegetarianism and veganism are related to an increased risk of disordered eating due to overlapping similarities in dietary rules. But previous research does not necessarily support this idea. 

Furthermore, previous literature has suggested eating disorder tools may be picking up on normal vegetarian and vegan-motivating food behaviours. This could result in inaccurate estimates of eating disorder prevalence in these populations.

Ms Courtney McLean is a PhD student in Central Clinical School’s Department of Psychiatry, whose research is on whether measures of eating disorder psychopathology are appropriate for vegans.

She said, “I and my co-authors Professor Jayashri Kulkarni and Dr Gemma Sharp aimed to conduct the first systematic review to examine the complex relationship between vegetarianism, veganism, and disordered eating. We also looked to examine the validity and reliability of commonly used eating disorder tools for use in vegetarians and vegans.”

The authors searched electronic databases MEDLINE, PsycINFO, and CINALH for literature published until June 2021, resulting in 48 eligible studies included in the review. Ultimately, Courtney said, their review was unable to confirm whether vegetarianism or veganism is associated with higher levels of disordered eating.

However, most studies reported a positive association between vegetarianism, veganism, and orthorexia nervosa, a form of disordered eating characterised by an obsession to eat “clean” and “pure” foods.

A limited number of studies reported on the validity and reliability of eating disorder tools in vegetarians and vegan. Overall, Courtney said, they found poor results across both disordered eating and orthorexia nervosa tools.

“This review highlights the degree to which vegetarians and vegans have been highly understudied within the eating disorder field,” said Courtney. Due to a heavy reliance on poor quality cross-sectional studies to date, she said, “future research is needed to establish a potential causal relationship between vegetarianism, veganism, and disordered eating. Without such research, it is unclear if vegetarianism or veganism increases the risk of developing disordered eating, or developing disordered eating increases the chances of transitioning to a vegetarian or vegan diet.”  

The results from the article raise important clinical implications for the eating disorder field. Until future research is established, it remains important for clinicians to gain an in-depth understanding of vegetarian and vegan patients’ motivations around food exclusion. It is also important for clinicians to enquire about how the vegetarian or vegan diets fit into a patient’s history of disordered eating. This will ultimately ensure their eating habits are not being over-pathologised for simply following a vegetarian or vegan diet.

As both vegetarianism and veganism are proving to be more than just a passing fad, future research is vital to untying the complex relationship between disordered eating, and vegetarian and vegan eating behaviours and attitudes.

Dr Gemma Sharp, senior author on the review, said, "Although further research is needed, the findings from this review challenge long-held beliefs that following a vegetarian/vegan diet is a risk factor for the development of an eating disorder. Instead, the link with eating disorder development appears to be the individual's motivation for pursuing a vegetarian/vegan diet in the first instance."

Reference

McLean CP, Kulkarni J, Sharp G. Disordered eating and the meat-avoidance spectrum: a systematic review and clinical implications. Eat Weight Disord. 2022 Jun 21. doi: 10.1007/s40519-022-01428-0. Epub ahead of print. PMID: 35729472.