Background: Gastric sensorimotor dysfunction, psychosocial factors and somatisation are all implicated in symptom generation in functional dyspepsia (FD). Aim: To determine the relative contribution of each of these factors to overall dyspeptic symptom severity and weight loss in FD. Methods: In 201 consecutive tertiary care patients with FD (mean age 40.1 (SD 12.6) years), gastric sensorimotor function was studied using barostat (sensitivity, compliance and accommodation). Psychosocial factors (depression and anxiety disorders, positive and negative affect, perceived stress, alexithymia and history of abuse), somatisation and co-morbid irritable bowel syndrome (IBS) and chronic fatigue symptoms were assessed using self-report questionnaires. Variables were correlated with dyspepsia symptom severity (DSS) and weight loss. Hierarchical multiple linear regression was used to identify determinants of DSS and weight loss. Results: Multiple linear regression identified the following determinants of DSS: gastric sensitivity (β = 0.77, p = 0.25), depression (β = 0.12, p = 0.06) and somatisation (β = 0.48, p2 = 0.29, p2 = 0.42, pConclusion: Symptom severity and weight loss in FD are determined by psychosocial factors (depression, abuse history) and somatisation, and only to a lesser extent by gastric sensorimotor function. The importance of psychosocial factors and somatisation compared to gastric sensorimotor function is most pronounced in hypersensitive patients.