Management of Constipation in Eating Disorders—A Scoping Review

ABSTRACT

Background

Constipation is a common nutrition impact symptom experienced by the eating disorder population.

Objective

The aim of this scoping review was to identify current recommendations and evidence for managing constipation within the eating disorders population, specifically anorexia nervosa (AN) and bulimia nervosa (BN).

Method

Using a scoping review framework, a search of relevant databases (MEDLINE (Ovid), Cinahl, Web of Science and Embase) was undertaken using MESH terms. Keywords included: feeding and eating disorders', constipation', gastrointestinal disease'. Reference lists and grey literature were searched. Studies were included if they included a discussion on constipation management in eating disorders and published in English. Data was extracted from the papers; management options were categorized based on common themes.

Results

Twenty‐eight studies met inclusion criteria. Suggested management strategies from articles were categorized into five themes: weight restoration (including regular eating), fibre, fluid, medication (including laxative withdrawal) and education. The strongest recommendations are that normalization of weight positively reduces rates of constipation within four to twelve weeks. There is some consistency in recommendations for increased fibre intake, increased fluid intake, medication use and patient education, but conflicting recommendations on laxative withdrawal.

Discussion

There is strong evidence to support for the role of weight restoration in the management of constipation in AN and BN. This is an area that needs more specialized research and practical recommendations particularly in regard to fibre, fluid, medication use, cessation of laxatives and patient and clinician education.

Summary

• Constipation is a complex and common symptom experienced in AN and BN.

• There are no clear guidelines specifically for the management within this population.

• This review aimed to identify current evidence for the management of constipation within AN and BN. It highlights the importance of weight restoration in treating constipation for this patient cohort.

1. Introduction

Eating disorders is a broad term that encompasses several diagnoses including anorexia nervosa (AN) and bulimia nervosa (BN) [1]. Their global incidence is increasing [2], and often results in gastrointestinal disturbances [3, 4]. Gastrointestinal symptoms can distract, delay, and complicate the ability to treat the eating disorder itself [5].

Defining constipation in this cohort can be challenging due to the subjective nature of constipation [6]. Self‐reported rates of constipation in the general population are higher compared to the medically defined criteria [6], noting that no definitions exist for AN and BN specifically. The Rome Foundation has defined functional constipation as a functional bowel disorder and also acknowledges opioid‐induced constipation. While we don't fully understand the mechanisms for constipation in AN and BN, these definitions may be useful in establishing objective markers of constipation in the AN and BN cohorts [6]. Technically, functional constipation within the current Rome IV criteria is defined as ‘symptoms of difficult, infrequent, or incomplete defecation predominate, and symptom onset occurring at least 6 months before diagnosis and symptoms present during the last 3 months’, with further diagnostic criteria [6].

Constipation is a common symptom in many people living with an eating disorder [7]. There is a variation in the incidence of constipation across the type of eating disorder. In particular 67%–83% of people diagnosed with AN and 63% of people diagnosed with BN report having symptoms of constipation [8]. It remains the most common lower gastrointestinal symptom reported in AN patients [5, 9]. Several factors contribute to the high incidence of constipation in this population.

Firstly, anxiety around feelings of bloating or fullness can lead to over‐estimating the symptoms of constipation [5, 10]. This is particularly prevalent during the initial refeeding phase of eating disorder management [11]. Hence the definition of constipation and what would be considered ‘normal’ bowel movements may be quite different within this patient group [12, 13]. This exaggerated concept of constipation often results in requests for laxative medications to manage discomfort as well as the patients' likely belief that this will also reduce energy absorption [14]. Hence the withdrawal of laxatives in this patient group needs careful management, as it often contributes to gastrointestinal changes and anxiety. Methods for laxative weaning can include immediate cessation of all types of laxatives, or they may be weaned slowly. At present it is not clear whether one method should be preferred over the other.

In addition to altered perceptions of gut function, physiological changes may also impair gut motility. Firstly, malnutrition is a common feature within eating disorders, particularly AN and BN [15]. The impact of malnutrition on gut pathophysiology is still largely unknown but previous research has shown that gastric emptying [16], small bowel transit time [15], whole gut transit [17] and colonic transit time [18, 19] are all delayed in this cohort. This slow gut motility seen in AN and BN may lead to or worsen symptoms of early satiety, bloating, nausea and ongoing constipation [20, 21].

Secondly, purging, including vomiting and laxative abuse, can lead to pelvic floor dysfunction and rectal prolapse [22, 23, 24]. Misuse of laxatives and laxative dependence can also lead to worsening constipation upon cessation [25].

Lastly, medications commonly used in the treatment of eating disorders may also contribute to an increased incidence of constipation, such as serotonin 5‐HT₃ receptor antagonists (e.g., ondansetron), tricyclic antidepressants (e.g., amitriptyline), anxiolytics (e.g., buspirone), antipsychotics (e.g., clozapine) and iron supplements (e.g., ferrous sulfate). All have been known to cause either early satiety, postprandial fullness and/or constipation [26, 27, 28, 29, 30].

There is currently a lack of guidance for clinicians in the management of gastrointestinal symptoms in the eating disorder patient. This may mean that patients are unnecessarily prescribed laxatives without considering other management strategies that may be of benefit for the patient. For this reason, a scoping review was conducted to systematically map the research done in this area. Hence the aim was to identify current recommendations and evidence for managing constipation within the eating disorders population, specifically anorexia nervosa (AN) and bulimia nervosa (BN) across inpatient and outpatient settings). This scoping review will also identify research gaps in the current literature related to constipation management.

2. Methods

2.1. Design

A scoping review was undertaken applying a combination of the original methodological framework of Arksey and O'Malley [31] including the five‐step process. In addition to recommendations from Levac et al. 2010 [32] and updated scoping methodology from JBI [33]. The PRISMA‐ScR Checklist [34] is included as supporting Information. A scoping review was chosen due to the lack of interventional evidence in this area, with no clear guidelines on how to manage constipation in this cohort. A review protocol was not registered.

2.2. Research Question

Using the PCC (Population, Concept and Context) construct [35], this scoping review aimed to identify current recommendations and evidence for the management of constipation within the eating disorders population, specifically AN and BN (Table 1). For the scope of this review, ‘eating disorders’ refers to clinically diagnosed AN and BN.

Table 1.

PICO acronym of research question for this scoping review.

Population	Concept	Context
Patients with anorexia nervosa or bulimia nervosa (any age)	Symptoms of reported constipation	Inpatient or outpatient setting

2.3. Search Strategy

The latest search was conducted on 23 August 2024 in a total of four electronic databases including: MEDLINE (Ovid), Cinahl, Web of Science and Embase. Search strategies were enabled by Boolean operators (AND, OR), medical subject headings (MESH) and descriptive key‐terms where appropriate. The search was piloted and due to the small number of papers in this area, a broad search strategy was used. Table 2 below, details the Medline search terms and keywords used. Initially, more specific search terms were trialled (e.g., specifying only AN or BN) however, this returned minimal papers. In addition, a grey literature search was conducted to source guidelines and resources to assist in answering the aims of this review.

Table 2.

Medline search terms (23/08/2024).

Database	Search strategy
Medline	1. Constipation/ 2. Gastrointestinal Diseases/ 3. Feeding and Eating Disorders/ 4. 1 or 2 5. 3 and 4 (‘Feeding and Eating Disorders’ AND ‘Constipation’ OR ‘Gastrointestinal Diseases’)

2.4. Study Selection

Due to the limited number of high‐quality studies within this area, there was no restriction on study design, study quality or year of publication. The search was restricted to literature focused on eating disorders management, that included a discussion of constipation management and published in English. An additional search of grey literature, including reference lists was undertaken. Where papers referred to primary studies, these were included in the final selection as grey literature. All articles were managed in Endnote (Version X9, Clarivate, Philadelphia, USA). Grey literature was added to the pool of records. Initial screening of titles and abstracts was undertaken by BH and verified by SC to determine if the article met the inclusion criteria. To prevent errors, initially both BH and SC screened the same 50 articles and discussed eligibility until consensus was reached. This same process was utilised for assessing eligibility (i.e., full text screening, devising themes and level of evidence). The process can be viewed in Figure 1.

Figure 1.

PRISMA flow diagram, study selection including screening and reasons for exclusion.

2.5. Data Extraction and Collation

After removal of duplicates via Endnote, all remaining records were screened based on title and abstract. Papers were excluded if they were not eating disorders related, not constipation related, not constipation management related, not in English. A full text review was conducted if there was inadequate information in the title and abstract to determine inclusion. Once the final eligible articles were identified, each article was reviewed as per JBI scoping methodology [33], and the data extracted including source (author, year), type of research (expert opinion/nonsystematic literature review, systematic literature review, cohort study etc), level of evidence, type of eating disorder and if they provided a recommendation on the management of constipation. Once data was extracted from the papers, each paper was coded as to main topics covered, and themes were allocated based on frequency of topics. If a paper did not address all identified themes, it was left as ‘not discussed’ under that particular theme. Management options and recommendations were extracted for each of the main themes, including weight restoration, fibre intake, fluid intake, medication and patient education.

3. Results

The initial search retrieved 1787 results, and an additional six articles were identified through grey literature searching. After the removal of 156 duplicates, 1637 titles were reviewed, and 66 articles underwent a full text review. A further 38 studies were excluded after the full‐text review leaving 28 articles for inclusion in this review. Reasons for exclusion can be seen in Figure 1.

The earliest study was published in 1985, the latest in 2023. Of the 28 articles identified, 20 were based on expert opinion [4, 10, 14, 24, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51], three prospective cohort studies [11, 18, 52], one retrospective cohort study [47], one cross sectional study [53], one case series [19], and two systematic literature reviews [20, 54]. Twenty papers were from America [4, 10, 14, 18, 24, 36, 37, 38, 40, 41, 42, 44, 45, 46, 47, 48, 49, 50, 55]. Suggested management strategies from articles were categorised into five themes, including weight restoration (including regular eating), fibre, fluid, medication (including laxative withdrawal) and education as seen in Table 3.

Table 3.

Included articles, type of research, level of evidence, eating disorder type and recommendations.

Author	Type of research	Level of evidence	Eating disorder Type	Weight restoration	Fibre	Fluid	Medication	Patient education	Comments
Atkins (2023) [36]	Opinion paper	5c	Generic not specified	Not discussed	Not discussed	Not discussed	Medication review. First line agent should be osmotic laxative (e.g. polyethylene glycol) +/− stimulant laxative (e.g. bisacodyl, senna). Note high potential for abuse. Consider a secretagogue or prucalopride.	Normal bowel function	Refer to anorectal manometry where available. Brain‐gut behaviour therapy, including pelvic floor biofeedback therapy. Constipation defined.
Bern (2016) [37]	Opinion paper	5c	Generic not specified	Nutritional rehabilitation is the safest therapy for gastroparesis in patients with AN.	Not discussed	Not discussed	Stepped approach to weaning laxatives and use sparingly to manage constipation. Avoid stimulant laxatives. Use bowel motility medication (E.g. Bethanocol chloride, cisapride, domperidone, metoclopramide, erythromycin) for delayed gastric emptying [56, 57, 58, 59, 60].	Not discussed	Antidepressants, particularly tricyclic antidepressants, may delay intestinal transit [61]. Constipation not defined.
Brotman (1985) [38]	Opinion paper	5c	AN and BN	Not discussed	Following cessation of laxatives aim for a high fibre diet.	Not discussed	Cease laxatives if being abused. Avoid stimulant laxatives. Addition of bulk‐forming laxatives (e.g. Metamucil) and stool softeners. If bowels do not open for 5–7 days try magnesium hydroxide. Use of bowel motility medication.	Consequences of laxative abuse.	Constipation not defined.
Cavan (2010) [39]	Opinion paper	5c	AN and BN	Not discussed	Aim for an increase in fibre intake	Aim for an increase in fluid intake	Addition of a bulk‐forming laxative or stool softener as required. Avoid stimulant laxatives. Possible need for bowel motility medication (e.g., metoclopramide 5–10 mg three times a day before meals). Use of antispasmodics (e.g., mebeverine) to alleviate colicky abdominal pain, however reassurance and small, frequent food portions may be more successful.	Not discussed	Constipation not defined.
Chun (1997) [18]	Prospective Cohort study (n = 13) with control group	3c	AN	Increased food (and fibre) intake for 3 weeks improved colonic transit time in all participants.	Increased fibre to 25 g per day (and increased food intake) intake for 3 weeks improves colonic transit time in all participants.	Not discussed	Cease use of laxatives, prokinetic agents or enemas. Medications should only be considered if symptoms persist after eating a well‐balanced diet for 3 weeks.	Not discussed	Address refeeding before management of constipation. Constipation (chronic) defined.
Chiarioni (2000) [11]	Prospective cohort study (n = 12) with control group	3c	AN	Gradually increase energy intake up to ~8400 kJ/d over 4 weeks (resulting in 8.4 kg weight gain) saw normalisation of colonic transit time in 8 of the 12 participants.	Aim for at least 15–20 g fibre daily (high residue diet)	Not discussed	Cease use of laxatives, prokinetic agents or enemas.	Not discussed	Address refeeding before management of constipation. If no improvement in symptoms after weight restoration consider anorectal retraining techniques (anorectal motor impairment may be a cause of constipation). Constipation defined.
Colton (1999) [53]	Cross sectional study (n = 14)	3e	AN and BN	Not discussed	Not discussed	Take 250 ml water with bulk forming agents.	Structured stepped approach to cease laxatives and normalise bowel habits. Discontinue all stimulant laxatives, no wean/taper. Offer patient bulk‐forming laxative (Metamucil or Prodiem with 250 ml water each). If BNO at 4–5 days can add a stool softener. If BNO 10 days, a glycerin suppository can be added. If BNO 14 days, if need to rule out obstruction, can give enema. After this, wait 1 week before any further intervention.	Normal bowel function via a structured psychoeducational intervention.	Structured laxative withdrawal resulted in reduced laxative use at 20 months post intervention in 57% of patients. Constipation not defined.
Gaudiani (2016) [40]	Opinion paper with case report citing Chun (1997) [18],	5c	AN and BN	Aim for weight restoration to resolve constipation/normalise bowel motions [18].	Aim for a low fibre intake (consumption of high fibre foods worsens constipation)	Maintain hydration status	Stimulant laxatives can be stopped without tapering. Replace with osmotic laxatives such as polyethylene glycol (Up to 34 g (or double dose) 3x day).	Not discussed	Constipation not defined.
Harper (2004) [52]	Prospective blinded cohort study	3e	AN and BN	Not discussed	Aim for an increase in fibre intake.	Aim for adequate water intake; or increase in water intake.	Blinded laxative taper, stepped protocol. Cease stimulant laxatives, start non‐stimulant medications in a stepped protocol providing; docusate (stool softener), psyllium (bulk‐forming laxative), fruit lax, magnolax/cascara. If BNO 5–7 days rule out bowel obstruction.	Normal bowel function. Consequences of laxative abuse.	Laxative withdrawal specifically. Constipation not defined.
Hedrick (2022) [24]	Opinion paper citing Mehler (2017) [4]	5c	Generic not specified	Not discussed	Not discussed	Not discussed	Not discussed	Not discussed	Addressing refeeding will improve constipation [3, 4, 5]. Constipation not defined.
Hornberger (2021) [41]	Opinion paper citing Bern (2016) [37], Roerig (2010) [14], Sachs (2016) [48]	5c	Generic not specified	Aim for weight restoration to resolve constipation/normalise bowel motions [37].	Notdiscussed	Not discussed	If constipation continues after weight restoration, consider osmotic (e.g. polyethylene glycol 3350) or bulk‐forming laxatives. Avoid stimulant laxatives [14, 48]	Normal bowel function and reassurance that symptoms will improve with regular eating.	Constipation not defined.
Mehler (1996) [42]	Opinion Paper/Book Chapter	5c	AN	Aim for weight gain to improve antral motility and delayed gastric emptying.	Aim for intake of high fibre foods	Not Discussed	Temporary use of a prokinetic agent to improve colonic contractions.	Not discussed	Treatment of constipation requires patience. Constipation not defined.
Mehler (1996) [43]	Opinion Paper/Book Chapter	5c	BN	Not discussed	Aim for a high fibre diet	Aim for adequate hydration	If constipation continues after diet and fluid changes, consider non stimulating osmotic laxative (e.g., 30–60 mL lactulose) or a glycerine suppository.	Consequences of laxative abuse and what symptoms to expect following cessation e.g., fluid retention.	Exercise should be encouraged. Constipation not defined.
Mehler (1997) [10]	Opinion paper/book chapter	5c	AN and BN	Not discussed	High fibre diet—at least 20–30 g of dietary fibre should be added. A measurable amount, to improve compliance.	Ample hydration	Review medications, especially psychiatric medications (i.e., antipsychotics, antidepressants), calcium channel blockers, iron supplements, anti‐parkinsonian agents, oral opioids, antacids, antihistamines and bowel antispasmodics that can exacerbate constipation. Consider a dose reduction and use of less constipating alternatives. Occasional use of a prokinetic to reduce colonic transit time, e.g., cisapride 10–20 mg TDS before meals. If ongoing BNO despite measures, investigation of secondary causes. In BN, complete cessation of laxatives. If BNO 4–6 days use of an osmotic laxative e.g., lactulose 60 mL every 2/4 until BO. After the 3rd dose if BNO, clinically evaluate for complicating factors. Once BO, continue 30–60 mL 1–2x day for a few weeks. If no complicating factors, a prokinetic agent may be utilised.	Normal bowel function and reassurance that symptoms will improve with time and regular eating. Consequences of laxative abuse and what symptoms to expect following cessation (in BN).	Measuring serum calcium and thyroid‐stimulating levels can represent treatable metabolic causes of constipation. Exercise to increase colonic propulsive activity [62]. Trial all measures for 2–3 months, if ongoing intractable constipation refer to specialist for assessment of colonic motor function. Constipation defined.
Mehler (1999) [44]	Opinion paper/book chapter	5c	Generic not specified	Aim for weight restoration to resolve constipation/normalise bowel motions.	Not discussed	Not discussed	Cessation of laxative abuse	Normal bowel function.	Constipation not defined.
Mehler (2004) [45]	Opinion paper	5c	BN	Not discussed	Aim for intake of high fibre foods	Aim for an increase fluid intake	Bulk forming laxatives (e.g., psyllium), if ongoing constipation consider osmotic laxative (e.g., lactulose). Stool softeners are of little clinical value.	Normal bowel activity, symptoms will resolve in 10 days to 3 weeks. Consequences of laxative abuse.	Bulimia nervosa specific. Referring to withdrawal of laxatives. Regular exercise encouraged. Constipation not defined.
Mehler (2017) [4]	Opinion paper citing Chun (1997) [18], citing Norris (2016) [20]	5c	AN and BN	In AN: Aim for weight restoration to resolve constipation/normalise bowel motions [18, 20]. In BN: Not discussed	In AN: Aim for intake of low fibre foods to avoid bloating (10 g/day) In BN: Not discussed	In both AN & BN: Aim for adequate hydration	In AN: Polyethylene glycol (1–2 capfuls 1–3x day) or lactulose (30–60 mL 1–2x day). Rarely, use of a glycerine suppository to ‘jump start’ normal peristaltic motion. Abdo x‐ray to exclude bowel distention if ongoing constipation after adequate trial of medications. Avoid stimulant laxatives. Avoid treating constipation with bulk forming fibre containing laxatives. In BN: Cease stimulant laxatives, no need to taper, and start daily polyethylene glycol [63]. Rare use of glycerine suppository. If constipation ongoing after 3–4 days, short course of a mild non stimulating laxative with ample hydration.	In both AN & BN: Consequences of laxative abuse. In AN: Normal bowel function and reassurance that symptoms will improve with regular eating and weight restoration. In BN: Definition of constipation as defined by the Rome III Criteria.	In AN: Addressing refeeding. In BN: A judicious amount of exercise is also important. Distraction free 10–15 min on the toilet, elevating legs onto footstool. Constipation defined.
Mitchell (2013) [19]	Case series	4 d	AN	Introduction of a regular feeding plan to increase oral intake saw resolution of constipation over a 4–6 week period.	Aim for higher fibre intake through use of fibre supplements.	Aim for an increase fluid intake	Docusate sodium 200 mg daily. If no relief, trial of polyethylene glycol. Review need for medications that often worsen constipation such as antipsychotics, antidepressants and diuretics.	Not discussed	Over 2–3 months constipation will gradually improve. Constipation not defined.
Norris (2016) [20]	Systematic Literature Review of non‐RCTs	1b	AN	Weight restoration improves gastric motility and symptoms of constipation over a 12‐week and 22‐week timeframe.	Not discussed	Not discussed	Prokinetics; ‐Domperidone improves gastric emptying (10 mg TDS for 14 days) [59], ‐Cisapride 8 mg 30 min pre‐meals [64] or 10 mg TDS for 6 weeks increases gastric emptying [57]‐Metoclopramide 10 mg IM [65] Metoclopramide is suggested as the first line prokinetic therapy that should be considered for the treatment of gastroparesis symptoms, in addition to dietary therapy.	Not discussed	Constipation not defined.
Perez (2016) [46]	Opinion paper citing Chun (1997) [18], Colton (1999) [57], Harper (2004) [52]	5c	AN and BN	Aim for weight restoration to resolve constipation/normalise bowel motions in AN [18].	Not discussed	Aim for adequate hydration, particularly when treating laxative abuse [52, 53].	Treatment of laxative abuse using a protocol [52, 53]. Overall suggest bulk forming agents and non‐laxative aids. Stool softeners, such as docusate, can be helpful.	Normal bowel function, consequences of laxative abuse [52].	Adolescents. Psychological support. Constipation not defined.
Roerig (2010) [14]	Opinion paper citing Colton (1999) [53], Harper (2004) [52]	5c	AN and BN	Not discussed	Not discussed	Not discussed	Utilising a protocol such as Harper 2004 [52] or Colton 1999 [53].	Education as per Harper 2004 [52].	If has an ED, an appropriate treatment plan for the particular ED should be enacted. Constipation not defined.
Ross (2007) [47]	Opinion paper with case review	5c	AN, BN, binge eating disorder, compulsive overeating	Not discussed	Not discussed	Not discussed	Use of a probiotic in chronic constipation for minimum 2 weeks reduced severity of constipation [66] (generic advice, not in eating disorder patients).	Not discussed	Case study discussed reports a decrease in constipation during her treatment (mixture of vitamin supps, exercise program, liquid meal replacement with 1200 calorie meal plan (increasing food and decreasing liquid gradually), a MV with copper, digestive support, digestive enzymes, probiotics. With a discharge weight of 90% of her ideal body weight. Constipation not defined.
Ross (2008) [55]	Retrospective cohort study	3c	Generic, not specified	Not discussed	Not discussed	Not discussed	Use of a plant based digestive enzyme at mealtimes and a daily probiotic supplement (Lactobacillus rhamnosus) reduced symptoms of constipation (not statistically significant), leading to less use of conventional medications for constipation. If patients still reported constipation after 2–3 days, prescribed conventional constipation medications.	Not discussed	Note medications such as Trazodone can effect constipation. Constipation not defined.
Sachs (2016) [48]	Opinion paper citing Colton (1999) [53],	5c	BN	Not discussed	Not discussed	Aim for adequate hydration	Cease stimulant laxatives and start daily osmotic laxative (polyethylene glycol) [67]. Use of a glycerine suppository or enema if BNO for a few days [68]. If ongoing BNO few days despite above, suggest abdominal x‐ray before initiating stronger agents.	Normal bowel activity, may take weeks to restore normal bowel function [53]	Laxative abuse specifically. If over‐exercising is not part of the eating disorder behaviours, a judicious amount of exercise may be beneficial for restoring normal bowel function. Constipation not defined.
Sigman (2003) [49]	Opinion paper	5c	Generic, not specified	Aim for normalisation of diet.	Fibre supplementation	Not discussed	Recommends use of fibre, mineral oil or polyethylene glycol. Period of treatment is not usually long, as normal motility returns within a few weeks of normal eating in AN. Avoid agents that can be used to purge.	Not discussed	Children & adolescents. Constipation not defined.
Staller (2023) [50]	Opinion paper citing Chun (1997) [18],	5c	Generic, not specified	Delayed gastric emptying may improve with normalisation of eating patterns and weight gain in AN [18].	Not discussed	Not discussed	The secretagogues linaclotide [69] and lubiprostone [70] improve colonic transit time in constipated patients. Utilise constipation treatment for patients that meet criteria for chronic idiopathic constipation and IBS with constipation. Avoid cathartic laxatives (stimulants and secretagogues) and consider osmotic or prokinetic agents as first‐line therapy (author opinion). Prokinetics (cisapride [57] and erythromycin [58] shown to improve gastric emptying in AN. However erythromycin was not effective in [71].	Normal bowel function and reassurance that symptoms will improve with time and regular eating.	Anorectal manometry may be useful to identify patients with rectal evacuation disorders that may benefit from biofeedback or physical therapy. Constipation not defined.
Wakefield (2009) [51]	Opinion paper	5c	AN	A well‐balanced diet will resolve colonic transit time and symptoms after 4 weeks.	Aim for an adequate fibre intake	Aim for adequate hydration	Tapering laxative intake in a stepped approach is advised, as chronic laxative abuse may lead to faecal impaction.	Not discussed	Constipation not defined.
West (2021) [54]	Systematic Literature Review	1b	AN	Weight restoration (1.4 kg weight gain/week) and regular eating (1200–1800 kcal/day), significantly reduces symptoms of constipation [72]. Significant weight gain, 1500–2500 kcal/day reduced constipation [73]. Weight restoration (2000–3050 kcal/day depending on progress of weight gain), normalise eating habits in inpatient treatment program, led to reduction in lower gastrointestinal symptoms [74].	Inadequate evidence to guide recommendations on fibre intake.	Not discussed	Not discussed	Not discussed	Constipation not defined.

Note: BO bowels opened, BNO bowels not opened, TDS three times a day.

Eight papers (one retrospective cohort study [55], seven opinion [24, 36, 37, 41, 44, 49, 50]) made recommendations without specifying the type of eating disorder (AN or BN). Seven papers provided advice in relation to AN only (two systematic literature reviews [20, 54], two prospective cohort studies [11, 18], one case series [19] two opinion papers [42, 51]). Three opinion papers provided advice in relation to BN only [43, 45, 48]. Nine papers provided advice in relation to both AN and BN (one prospective blinded cohort study [52], one cross‐sectional study [53], one opinion paper with case report [40], six opinion papers [4, 10, 14, 38, 39, 46]). Ross [47], an opinion paper with case review referred to AN, BN, binge eating disorder and compulsive eating.

Five papers [4, 10, 11, 18, 36] defined constipation, most commonly diagnosed as per the current Rome Criteria relevant to the year the article was published, for example Chiarioni et al., 2000 utilised the Rome II criteria, Mehler 2017 utilised the Rome III criteria and Atkins 2023 the current Rome IV Criteria. The remaining 23 articles did not describe the definition used to define constipation. Three studies, one case series [19] and two expert opinion papers [10, 37], discussed the need to consider the constipating effect of other medications typically used in this cohort such as antidepressants, antipsychotics and diuretics. Mehler et al. (1997) highlighted those additional medications with constipating effects such as calcium channel blockers, iron supplements, anti‐parkinsonian agents, opioids, antacids, antihistamines and bowel antispasmodics should be reviewed, and a dose reduction or alternative be considered.

Two papers [52, 53] also recommended ruling out the possibility of a bowel obstruction, however the timing of this is unclear. Colton et al. (1999) suggests ruling out a bowel obstruction after 14 days with no bowel movement, while Harper et al. (2004) suggests investigating possible bowel obstruction after 5–7 days without any bowel movement.

3.1. Weight Restoration

Fifteen papers [4, 11, 18, 19, 20, 37, 40, 41, 42, 44, 46, 49, 50, 51, 54] recommended normalisation of weight (weight restoration, nutritional rehabilitation or refeeding) as a key aspect of addressing constipation and/or delayed gastric emptying. The majority of articles did not expand on this management strategy and were based on expert opinion. One cohort study reported increased food intake for 3 weeks improves colonic transit time [18] while another found a gradual increase in energy intake up to 8400 kJ per day for 4 weeks resulted in normalisation of colonic transit time in 8 out of 12 participants [11]. Both studies highlighted the need to address normalisation of food intake before management of constipation. One case series [19], found that introduction of a regular feeding plan with increased oral intake saw resolution of constipation over a 4–6 week period. Likewise, a systematic review of non‐randomised studies [20] found weight restoration improves gastric motility and symptoms of constipation over a 12 week and 22 week time frame respectively. Three studies within a systematic review of randomised studies [54] reported weight gain significantly reduces symptoms of constipation. One study quantified this recommending a weight gain of 1.4 kg per week to see improvements [72]. These studies show a strong recommendation that normalisation of weight positively reduces rates of constipation within 4–12 weeks.

3.2. Fibre Intake

Three cohort studies [11, 18, 52] and seven expert opinion papers [10, 38, 39, 42, 43, 45, 51] supported the use of a high fibre diet (15–25 g fibre per day) or a general increase in fibre consumption to help manage constipation. One expert opinion paper recommended fibre supplements [49] as did one case series [19]. No specific type of fibre supplement or dosage was recommended. Conversely, two expert opinion papers recommended a low fibre diet, to reduce bloating [4] and prevent worsening of the constipation [40]. West et al. (2021) concluded in their systematic review of randomised studies that there was inadequate evidence to support a recommendation around fibre intake and management of constipation [54].

3.3. Fluid Management

The majority of papers reviewed did not discuss fluid requirements. Of those that did, recommendations included an increase in fluid intake [19, 39, 45, 52] or to maintain adequate hydration [4, 10, 40, 43, 46, 48, 51]. No studies recommended a specific daily fluid intake goal or defined ‘adequate’ hydration.

3.4. Medications

Two cohort studies [11, 18] and two opinion papers [41, 43] recommended the use of medications only if symptoms of constipation persisted once weight was restored or regular eating was established. Eleven articles (one cohort study [52], ten opinion papers [4, 37, 38, 39, 40, 41, 43, 48, 49, 50]) recommended the avoidance of stimulant laxatives in this population, particularly in those with a history of laxative abuse. Five opinion papers [4, 10, 36, 40, 48] recommended use of an osmotic laxative as the first line of intervention if commencing a laxative. One case series [19] and five opinion papers [38, 39, 41, 45, 46] recommended an osmotic laxative, stool softener or a bulk forming laxative. One cohort study [55] and one opinion paper [47] recommended use of a probiotic before use of conventional medications for constipation. Two papers recommended the use of a suppository or enema [9, 48].

One systematic review [20] and six opinion papers [10, 37, 38, 39, 42, 50] recommended use of prokinetics. There was limited documentation about the type, timing and dosage. Cavan et al. (2010) recommended metoclopramide 5–10 mg three times per day before meals and Mehler et al. (1997) recommended cisapride 10–20 mg three times per day before meals. Norris et al. (2016) in their systematic review of non‐randomised studies concluded that gastric emptying improved with (i) domperidone 10 mg three times per day for 14 days [59], (ii) cisapride 8–10 mg 30 min before meals [57, 64], and (iii) 10 mg of intramuscular metoclopramide [65]. Norris et al. 2016 noted caution when using cisapride and domperidone as both can have cardiac side effects in patients with severe malnutrition [75]. Norris et al. (2016) also commented that whilst prokinetics do improve gastric emptying, they may not be needed as improved dietary intake and weight restoration alone are sufficient to return gastric emptying to normal in most patients.

Two opinion papers [14, 46] recommended addressing laxative abuse using a protocol, as outlined in one cross‐sectional study [53] and one cohort study [52]. Colton et al. (1999) [53] recommended a laxative withdrawal protocol which involved ceasing all stimulant laxatives and a stepped approach of a bulk‐forming laxative, stool softener, glycerin suppository and enemas. Similarly, Harper et al. (2004) [52] also recommended ceasing all stimulant laxatives and a stepped protocol of a stool softener, bulk‐forming laxative and natural supplements.

Eight opinion papers [4, 10, 37, 38, 40, 45, 48, 51] recommended tapering stimulant laxative intake in a stepped approach and replacing with a non‐stimulant laxative. Two cohort studies [11, 18] state immediate cessation of laxatives is safe, and that all medications, including stimulant laxatives, non‐stimulant laxatives, prokinetics and enemas, should be ceased without the need for weaning. These studies recommend against the use of medications in the management of constipation and that the focus should be on increasing dietary intake and weight restoration.

3.5. Role of Education

Twelve studies (one cohort study [52], one cross sectional study [53], and ten opinion papers [4, 10, 14, 36, 41, 44, 45, 46, 48, 50]) recommended education about normal bowel activity and reassurance that symptoms will improve with time and regular eating. Seven articles (one cohort study [52] and six opinion papers [4, 10, 38, 43, 45, 46]) discussed educating the patient on the consequences of laxative abuse and what symptoms to expect following cessation.

Additional therapies were recommended in three studies. Chiarioni et al., (2000) recommended anorectal retraining techniques if constipation continued after weight restoration [11] and Atkins et al. (2023) recommended referral for anorectal manometry and brain‐gut behaviour therapy [36]. Additionally Staller et al. (2023) recommended referral for anorectal manometry to identify patients with rectal evacuation disorders that may require biofeedback or physical therapy [50].

4. Discussion

The aim of this study was to identify current evidence and recommendations for the management of constipation within an adult AN and BN population. Overall, there is strong evidence to support the role of weight restoration in managing constipation. Beyond this there is a lack of evidence to support other specific constipation management strategies due to varying and low‐quality recommendations.

There is strong evidence through systematic reviews and expert opinion supporting the role of weight restoration as pivotal in the management of constipation within this patient group. However, it is not so clear as to how long it will take to see resolution in symptoms of constipation and how much weight gain is required to achieve a benefit. Some authors suggest constipation will resolve within 4 weeks [11, 19, 54], while others suggest this may take up to 22 weeks [20]. Current evidence suggests only a small increase in weight per week of 1–2 kg will improve symptoms of constipation [72]. Weight restoration can be attempted before the introduction of medications [11, 18, 41, 43] such as laxatives or prokinetics [20]. Other strategies may be considered where weight restoration alone does not resolve symptoms of constipation, where an attempt at weight restoration has failed; or where symptoms of constipation need to be addressed immediately. While the majority of recommendations are not supported through interventional studies, there is some consistency within expert consensus.

Findings indicate that osmotic, bulk‐forming or stool softener laxatives and/or enemas are preferred when laxatives are required [4, 10, 19, 36, 38, 39, 40, 41, 45, 46, 48]. Stimulant laxatives should be avoided due to the high risk of misuse [4, 37, 38, 39, 40, 41, 43, 48, 49, 50, 52, 53] and potential for long term motility issues which could exacerbate constipation issues in the future [48, 53]. Objective measures of constipation are important as some patients may exaggerate reported symptoms to receive laxatives to achieve weight loss [14]. Laxatives need to be prescribed with care and ceased if being misused. Study results highlight the inconsistency related to how laxatives should be ceased in cases of long‐term laxative abuse; whether they should be ceased without weaning or tapered in a stepped approach and replaced with a non‐stimulant laxative.

A systematic review [20] and six opinion papers [10, 37, 38, 39, 42, 50] did recommend prokinetic agents to speed up gastric motility and subsequently preventing symptoms of ongoing constipation. There is general consensus that a prokinetic drug administered 30 min before mealtimes may be beneficial [10, 20, 39]. More research is required to explore the type, timing and dosage of prokinetic usage. Of particular importance but not discussed in many papers is the need to rule out other possible reasons for bowel dysfunction. This may include the use of abdominal x‐ray after 5–14 days with no bowel movement [52, 53] to ensure there is no faecal loading or obstruction; and also identification of medications that may affect bowel function [10, 19, 37]. It is not always possible to remove or cease medications that may be exacerbating constipation due to the complexity of eating disorders and high rates of comorbid mental health illness [76]. Clinicians should minimise medications with constipating effects, and where this is not possible, a clear management plan should be provided to address constipation such as regular screening for constipation and the use of prophylactic laxatives [26]. Clinicians may need to review the benefit versus harm of such medications, possible alternative non‐constipating options, a dose reduction and whether there is a need to prescribe non‐stimulant laxatives for patients requiring these medications [10].

There was overall consensus, however from very low‐level evidence (expert opinion and cohort studies), on ensuring adequate or increased fibre intake [10, 11, 18, 38, 39, 42, 43, 45, 51, 52]. These recommendations lacked specific detail around type and amount of fibre, some papers suggested between 15 and 30 g fibre per day [10, 11, 18]. The dietary fibre recommendations for adult women and men in Australia are 25 and 30 g respectively, which supports general healthy eating advice for the general population [77]. Increasing fibre intake beyond what is considered ‘normal’ or ‘adequate’ needs to be balanced against the risk of worsening symptoms of early satiety and bloating [4] and any tendency towards over‐consumption of high‐fibre low‐energy foods (e.g. vegetables, legumes, fruit) which may delay ongoing weight restoration [78]. In addition, adequate hydration assists in regulating bowel motions [79] but must be carefully monitored given the risk of restricting fluid intake (including purging) or overloading as a means to falsify weight or suppress hunger [80]. More research is needed to provide specific recommendations.

Patient support and education may also be beneficial. It is not unusual for a person living with an eating disorder to have a distorted view of what normal bowel motions are and also have a low threshold to bloating, making it difficult to diagnose constipation [5, 10]. This was clear in the findings from this review, in which many papers did not use a clear definition of constipation and of the papers that did it is noted that the definition per the Rome criteria has evolved over time. Clear objective markers will be important for diagnosis but as highlighted in the findings of this scoping review there is expert consensus for education of patients on normal bowel function, and the role of weight restoration in resolving and preventing constipation. Education of patients should involve topics such as risk of laxative abuse, the definition of constipation as per the Rome IV Criteria [6] and reassurance that symptoms will improve with weight restoration and regular eating. In an outpatient setting it has been identified that nutritional counselling is a key component in management of GI symptoms [81]. Clinician education was not addressed in any study. Clinician education in identifying constipating agents, appropriate prescribing of laxatives and appropriate use of psychoeducation is essential [78]. Future guidelines should address both patient and clinician in education.

The major limitation of this study is the inability to provide clear guidance around the management of constipation in this cohort due to the low level of evidence with the majority of included studies based only on expert opinion, providing varied and vague management strategies with few specific recommendations. A limitation of using expert opinion papers is that recommendations may appear stronger where experts have published multiple papers on the topic. Similarly, this review included original papers and review papers, again resulting in the possibility of over‐emphasizing recommendations. To ensure clarity, cited papers specifically mentioned in review articles have been documented in Table 3. In addition to this, the evidence is lacking in regard to specific management strategies for all types of eating disorders, the papers reviewed do not include emerging diagnoses such as Avoidant/Restrictive Food Intake Disorder and Disorders of Gut‐Brain Interaction (DGBI). It is known that there is a large overlap between eating disorders and DGBI [82]. Given the lack of published data in this area, methodological limitations included a broad search strategy and many opinion papers only refer to a very small research base, leading to a duplication of these findings. There is wide scope for future research focused on clearly defining constipation in these cohorts along with interventional studies assessing both individual bowel management strategies, and also multifaceted clinical management pathways. Of specific interest are areas that have a clear lack of consensus such as protocols for ceasing long term laxative use. However, the findings from this study have clinical benefit in supporting consensus in favour of the role of weight restoration in the management of constipation.

Management of constipation within the eating disorders population is complex and if not managed correctly has the possibility of doing greater harm. There is strong evidence to support prioritising weight restoration as a key factor in ensuring bowel function returns to normal. Weight restoration is not only critical for overall health, but also for normalisation of bowel movements. There is only very weak (expert opinion) evidence to support other treatment strategies to manage constipation within the eating disorders population. These include the use of osmotic or bulk‐forming or stool softener laxatives and/or enemas, prokinetics, adequate dietary fibre and fluid intake, and patient education. Further research is needed to enable the development of an evidence‐based treatment protocol to guide clinical management of constipation within this patient group, and more broadly the management of GI symptoms [78].

5. Conclusion

Constipation is prominent and complex condition experienced within the eating disorder population. There is strong evidence to support the role of weight restoration in managing constipation in AN and BN. Specific recommendations regarding fibre, fluid, medication use, cessation of laxatives, patient and clinician education are needed to help clinicians and improve quality of patient care. Further research is needed to investigate management of constipation in this cohort to inform appropriate clinical guidance and protocols.

Author Contributions

B.H. and S.C. contributed to the conception and design of the research, the acquisition, analysis, and interpretation of the data. B.H. drafted the manuscript and S.C. critically revised the manuscript; and B. Heathcote agrees to be fully accountable for ensuring the integrity and accuracy of the work. All authors read and approved the final manuscript.

Ethics Statement

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Peer Review

The peer review history for this article is available at https://www.webofscience.com/api/gateway/wos/peer-review/10.1111/jhn.70100.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.