OBJECTIVES: This review focuses on the relationship between obesity and aging 
and how these interact to affect cognitive function. The topics covered are 
guided by the Scaffolding Theory of Aging and Cognition (STAC [Park and 
Reuter-Lorenz. Annu Rev Psychol 2009;60:173-96]-a conceptual model designed to 
relate brain structure and function to one's level of cognitive ability.
METHODS: The initial literature search was focused on normal aging and was 
guided by the key words, "aging, cognition, and obesity" in PubMed. In a second 
search, we added key words related to neuropathology including words 
"Alzheimer's disease," "vascular dementia," and "mild cognitive impairment."
RESULTS: The data suggest that being overweight or obese in midlife may be more 
detrimental to subsequent age-related cognitive decline than being overweight or 
obese at later stages of the life span. These effects are likely mediated by the 
accelerated effects obesity has on the integrity of neural structures, including 
both gray and white matter. Further epidemiological studies have provided 
evidence that obesity in midlife is linked to an increased risk for Alzheimer's 
disease and vascular dementia, most likely via an increased accumulation of 
Alzheimer's disease pathology.
CONCLUSIONS: Although it is clear that obesity negatively affects cognition, 
more work is needed to better understand how aging plays a role and how brain 
structure and brain function might mediate the relationship of obesity and age 
on cognition. Guided by the STAC and the STAC-R models, we provide a roadmap for 
future investigations of the role of obesity on cognition across the life span.