Epidemiologic studies show that weight loss is commonly associated with Alzheimer's disease. It would be a manifestation of the disease itself. It is not easy to explain weight loss as subjects with Alzheimer's disease have adequete caloric intakes. Several hypothesis are considered: increased energy expenditure, biologic disturbances, dysfunction in body weight regulation, mesial cortex temporal atrophy. However, at the present time, no study can give a proper explanation. The amelioration of nutritional problems, which lead to many complications (infections, bedsores, bedridden subjects, etc), could be one of the best strategies to lessen the burden of the disease.