Reduced cerebral glucose metabolism, as measured by FDG-PET hypometabolism, is associated with accelerated cognitive decline in older adults.

Study: Lewy body pathology exacerbates brain hypometabolism and cognitive decline in Alzheimer’s disease

In older adults with memory problems, those who have two types of brain damage (Alzheimer’s and Lewy bodies) show worse brain energy use and faster memory loss than those with just Alzheimer’s. This proves that when the brain uses less sugar (glucose), thinking gets worse faster.

Study: The association between omega-3 supplementation and cognitive decline in older adults

This study found that taking omega-3 supplements was linked to faster memory loss in older adults, and the reason appears to be that their brains started using less sugar (glucose) for energy — which is exactly what the claim says happens when people decline cognitively.

Study: CSF tau protein and FDG PET in patients with aging-associated cognitive decline and Alzheimer’s disease

This study found that older adults with early memory problems have lower brain energy use in areas linked to thinking and memory, which means less glucose is being burned there—this matches the idea that brain energy loss is tied to faster thinking decline.