A review of the scientific literature on Parkinson's disease, conducted by SISSA research scientists, shows that even the non-motor symptoms associated with the disease can contribute to the changes in body weight seen in patients (including those subjected to deep brain stimulation).

Among the factors affecting eating habits and body weight there could be, for example, an impaired ability to derive pleasure from food and changes in motivation. These are important findings which can help to understand how to reduce these effects of Parkinson's that exacerbate an already negative clinical situation.

Patients affected by Parkinson's disease often show marked changes in body weight: they may gain or lose a lot of weight depending on the stage of the disease, or they may put on up to ten kilos after deep brain stimulation (a treatment to alleviate the symptoms).

This situation considerably worsens the quality of life of a person who is already suffering from heavily disabling motor disorders, so it is important to understand what are the factors that cause it.

"The body weight and eating habits of Parkinson's patients change as the disease progresses," explains Marilena Aiello, SISSA researcher and first author of the study published in the journal Appetite. "In our paper, we reviewed studies on Parkinson's that provided data on the association between non-motor symptoms and dietary habits and body weight. This way, we were able to evaluate some factors which, beyond the motor symptoms and drug treatments, might play a role in this problem."

Depression, cognitive impairment, sensory disturbances -- chiefly smell and taste -, impaired ability to feel pleasure: all these aspects contribute to incorrect eating habits.

"The possible role of the ability to feel pleasure and motivation towards food consumption is particularly interesting. Parkinson's patients may be somewhat lacking in this respect and therefore eat less and lose weight, whereas the weight gain exhibited after deep brain stimulation seems to point to an increase in pleasure and motivation associated with food. Specific studies are required to confirm or refute this finding emerging from the literature review."

"Studies like ours can help those working with these patients: awareness of the roles played by the different factors is in fact crucial for devising interventions aiming to minimise the effect of the deficits and restore normal weight levels in individuals who are already suffering because of the disease."