Unintended weight loss frequently complicates the course of many neurodegenerative disorders and can contribute substantially to both morbidity and mortality. This will be illustrated here by reviewing the characteristics of unintended weight loss in the three major neurodegenerative disorders: Alzheimer’s disease, Parkinson’s disease and Huntington’s disease. A common denominator of weight loss in these neurodegenerative disorders is its typically complex pathophysiology. Timely recognition of the underlying pathophysiological process is of crucial importance, since a tailored treatment of weight loss can considerably improve the quality of life. This treatment is, primarily, comprised of a number of methods of increasing energy intake. Moreover, there are indications for defects in the systemic energy homeostasis and gastrointestinal function, which may also serve as therapeutic targets. However, the clinical merits of such interventions have yet to be demonstrated.