Studies have shown that overweight people are more likely to develop Alzheimer’s disease years later than normal-weight middle-aged adults. But researchers have also found that people in the early stages of Alzheimer’s disease are more likely to have a lower body mass index. A current study examined the relationship between Alzheimer’s disease and body mass index. The findings were published in print on Nov. 22, 2011, in Neurology, the medical journal of the American Academy of Neurology. The 506 people enrolled in the study were monitored with advanced brain imaging techniques, and their cerebrospinal fluid was analyzed for a biological marker of Alzheimer’s disease. The marker can be present for years before the first symptoms of Alzheimer’s manifest. The participants, in part, were people with Alzheimer’s. The study was neuroimaging-led and the population was divided into four groups, including people with no memory impairment, mild cognitive impairment, moderate memory impairment and Alzheimer’s patients. The study found that among people with no memory or thinking impairment and those with mild cognitive impairment, those in whom biomarkers of Alzheimer’s disease were present had a lower body mass index than those who did not have the markers. For example, for people with mild cognitive impairment and a body mass index of less than 25, the characteristic Alzheimer’s biomarker β-amyloid sheet was present in the cerebrospinal fluid of 85% of the population. By comparison, it was found in only 48% of people with mild cognitive impairment who were overweight. This difference was also reproduced in the population with no memory or thinking disorders. “These results suggest that brain tissue changes in the ultra-early stages of Alzheimer’s disease are associated with systemic metabolic changes,” commented study author Jeffrey M. Burns, M.D., M.S., a member of the American Academy of Neurology and a member of the University of Kansas City School of Medicine. This result may be due to disease damage to a region called the hypothalamus, which plays a role in regulating metabolism and food intake. Further studies should investigate whether this correlation reflects a systemic response to an as-yet-unknown disease, or whether it is a distinctive feature that leads to a predisposition to disease.