When the brain uses less sugar for energy, older people tend to forget things or think more slowly than they used to.

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.

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.

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.