there are several theories out there to explain the connection between high blood sugar and dementia. Diabetes can also weaken the blood vessels, which increases the likelihood that you’ll have ministrokes in the brain, causing various forms of dementia. A high intake of simple sugars can make cells, including those in the brain, insulin resistant, which could cause the brain cells to die. Meanwhile, eating too much in general can cause obesity. The extra fat in obese people releases cytokines, or inflammatory proteins that can also contribute to cognitive deterioration, Roberts said. In one study by Gottesman, obesity doubled a person’s risk of having elevated amyloid proteins in their brains later in life.