The most challenging presentation of severe or refractory FD is when accompanied by substantial dietary restriction, weight loss or malnutrition. In tertiary care, weight loss in FD is strongly associated with early satiation, and also nausea and vomiting, but its predictive value for underlying organic disease is limited.
281 Weight loss is more strongly associated with depression, a history of abuse, and somatisation than with gastric sensorimotor function, especially in viscerally hypersensitive patients,
282 with more frequent physician visits and reduced quality of life,
283and is more frequent in female patients with overlap of FD and IBS.
114
In patients with FD and restricted diet or weight loss it is vital to screen for ARFID, and other eating or feeding disorders, to assist with behavioural management.
179 252 ARFID is a feeding and eating disorder described recently in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders.
284 There is a substantial overlap with DGBI, especially those with dyspepsia, nausea, vomiting, or abdominal pain components.
285 Indeed, patients with FD frequently meet criteria for ARFID, irrespective of alterations in gastric emptying.
179 This suggests that the restricted eating patterns reported by patients with FD may actually be driven primarily by ARFID. Unlike anorexia nervosa and bulimia, ARFID is not driven primarily by concerns about body shape or weight, but rather by other core motivations, of which fear avoidance of gastrointestinal symptoms is the most prevalent in DGBI.
285 However, the precise relationship between DGBI and ARFID remains to be determined.
285 These may be different names for the same presentation, separate comorbidities that frequently coexist, or else ARFID may develop secondary to a DGBI in some individuals.
285 Caution has been advised regarding the risks of giving overly restrictive and avoidant dietary advice in DGBI,
286 because ARFID may often go unrecognised. Moreover,
nasogastric tube feeding may impair both nutritional rehabilitation and psychological recovery in ARFID.
287 In contrast with some dietary approaches for FD, which avoid specific foods or reduce food volume,
exposure-based CBT helps patients with ARFID re-build tolerance to specific foods and food volume systematically and gradually, decreasing fear and anxiety related to precipitating gastrointestinal sensations or symptoms, while regulating hunger satiety cues.
179
Early dietitian involvement should, therefore, be considered to avoid over-restriction of diet in severe or refractory FD.
288 Optimised oral nutrition is the best management option for most patients. If, and when, to escalate to clinically assisted nutrition or hydration support is a finely balanced risk versus benefit decision, which should be made in a multidisciplinary nutrition support team setting, and driven primarily by objective markers of malnutrition, rather than by severe symptoms alone.
289 In terms of optimising weight, in a small RCT recruiting 34 patients with FD, without anxiety and depression and not on antidepressants, mirtazapine improved early satiation, quality of life, gastrointestinal-specific anxiety, nutrient tolerance and weight loss significantly, compared with placebo,
225but this requires confirmation in larger studies before widespread adoption in clinical practice.
290