Weight loss is a nutritional problem commonly associated with Alzheimer disease. Two types of weight loss have been described. A severe weight loss correlated with a decrease in daily caloric intake and with increased difficulties in performing the activities of daily living. A slowly progressive but clinically significant loss, not associated with either a decrease in caloric intake or an inflammatory syndrome. It is difficult to explain this type of weight loss as subjects have adequate caloric intakes. Several hypothesis are however considered as increased energy requirements (which can result from increased energy expenditure, from increased metabolic disorder, or from increased growth hormone secretion), or mesial temporal cortex atrophy. But, at the present time, no study can give a proper explanation. Vitamin deficiencies, specially vitamin B6, B12 and folates, high homocysteine level, antioxidants deficiencies (especially, vitamin E deficiency), iron, counter, and phenol derived could also influence the memory capacities and have an effect upon cognitive impairment, as reported in epidemiological studies. The prevention of nutritional deficiencies in patients with Alzheimer's disease, could be one of the strategies to improve the caregiver and the patients quality of life.