Involuntary weight loss is a symptom of protein energy malnutrition often reported among elderly people, especially those with dementia. In this study, we examined whether dementia-related eating difficulties increase the probability of weight loss in the elderly. This cross-sectional observation study was conducted in 60 community-dwelling elderly people with dementia (84.1±6.7 yr of age). Over 6 months, 26.7% of the subjects lost at least 5% of body weight. Impaired mental status and eating difficulties were closely associated with weight loss as determined by Spearman's rank correlation coefficient. Assessment of eating difficulties combined with mental states in the subjects by discriminant analysis enabled us to differentiate subjects with >=5% weight loss from those with less than 5% weight loss at a probability of 76.4%. This result suggests that eating difficulties and impaired mental status among elderly people with dementia are closely associated with weight loss.