Weight changes are often a side effect of an illness. Some illnesses, such as thyroid disorders, cause the patient’s weight to increase, while other disorders may cause weight loss. Patients with Parkinson’s disease, however, experience significant weight fluctuations of up to 25 pounds in both directions depending on what stage of the disease they are experiencing.

New research says that these weight gains and losses are normal. Author of the study, Marilena Aiello, says that the “eating habits of Parkinson’s patients change as the disease progresses.” They found a few factors that might contribute to these changes in dietary habits, including depression, cognitive impairment, and sensory disturbances that alter smell and taste. These factors can all contribute to loss of appetite and thus weight loss. The study also showed that, after deep brain stimulation therapy, patients may experience an increase in pleasure and motivation associated with food, resulting in an increase in appetite and subsequent weight gain.

Learn more about this study in this article from PsychCentral.