Does Parkinson's Disease Cause Weight Loss?
Yes, weight loss often occurs in patients with Parkinson's disease (PD). In one study, patients with Parkinson's disease lost an average of 7.7% of their body weight during the symptomatic period of disease. This figure was significantly higher than weight loss observed in the control group [1].
Parkinson's disease-related weight loss is usually caused by complications associated with the disease, such as difficulty swallowing (dysphagia), loss of appetite (anorexia), and gastrointestinal (GI) dysfunction. These symptoms can make it difficult for patients with Parkinson's to eat, resulting in insufficient energy intake to maintain a stable weight. Compounding this issue is the fact that patients with PD often expend increased amounts of energy due to prolonged muscle stiffness (rigidity), shaking (tremor), and medication-induced involuntary motions (for example, levodopa) [2]. Together, this decreased energy intake and increased energy expenditure result in significant weight loss.
Weight loss may also be caused by other Parkinson's disease-related comorbidities, such as mood disorders and depression. Medical complications, such as pneumonia and cancer, can also result in weight loss in patients with PD. Lastly, some anti-Parkinsonian medications may have the side effect of inducing weight loss [2].
Intriguingly, one study has suggested that weight loss can occur in patients even before the onset of PD symptoms or use of any medications. The authors of this study claim that, in some patients, weight loss begins several years prior to diagnosis and is not caused by decreased energy intake [3]. The reason for this phenomenon remains unclear, and further research is required to confirm the significance of this finding. However, this early weight loss in patients with Parkinson's may be of prognostic significance and could potentially indicate poor outcomes [4].