This document summarizes a roundtable discussion on the role of nutrition in Alzheimer's disease (AD). The discussion focused on how being overweight or obese in midlife may increase the risk of developing AD decades later, though evidence is conflicting. After midlife, higher body weight and BMI are associated with lower dementia risk. Weight loss and underweight in late life are linked to higher dementia risk. The natural trajectory of BMI over the lifespan differs between those who do and do not develop dementia. Changes in BMI and weight loss may also be associated with clinical progression of AD. Further research is needed to better understand these complex relationships between nutritional status and AD risk and progression.