An open-ended question: Alzheimer's disease and involuntary weight loss: which comes first?

After the onset of Alzheimer's disease (AD), a substantial percentage of patients experience involuntary weight loss (IWL), but there is some debate as to whether IWL is a cause or a consequence of AD. It may play a causal role, because nutritional deficiencies have been found to be associated with worsened cognitive performance, even in subjects without dementia. Conversely, it may be an effect of the disease, considering the hypothesis that the neurodegenerative process associated with AD may itself lead to IWL. The aim of the present review was to help to shed some light on the relationship between IWL and AD. We focus on the problem of the relationship between AD and IWL, and on which comes first. Even when external factors are well controlled, the association between IWL and the progression of AD seems, for the time being, to be unavoidable. In the light of the literature on the topic, we conclude that IWL is more a consequence than a cause of AD, although chronic diseases and disabilities are factors that may facilitate cognitive decline and accelerate the onset of AD if they are not adequately treated from the nutritional standpoint.