Objective To evaluate the correlation between changes in regional cerebral glucose metabolism and reduced body mass index (BMI) in patients with mild to moderate Alzheimer's disease(AD). Methods Regional cerebral glucose metabolism in many regions of interest of 27 AD patients were measured by positron emission tomography (PET) through 18 F fluro deoxyglucose (FDG) and their correlation with low BMI was analysed. Results The analysis using simple and multiple regression correlation showed that the metabolic ratio had a positive correlation with low BMI only in anterior cingulate cortex. Conclusions Anterior cingulate cortex may preferably involve in the regulation of food intake and body weight.