An impaired ability to regulate blood sugar is associated with shrinkage of a part of the brain involved in memory and learning.
The brain needs a rapid and constant supply of glucose to function at its best. Previous research has suggested that in diabetes, problems in glucose regulation could affect the brain's chemistry and lead to memory decline. In a new study, researchers at New York University have looked at a group of older healthy non-diabetic people, some of whom had elevated blood sugar.

They found that there was a clear link between high blood sugar and reduced volume of the hippocampus, a structure within the brain concerned with memory and learning. Those with impaired blood sugar regulation also showed a poorer performance on memory tests. But weight loss and exercise can both normalise blood sugar levels. So it may be that a healthy lifestyle can help keep your memory in trim, as well as your body.