Diabates can harm the brain either indirectly, through vascular damage, or directly through nerve cell degeneration. The latter is a less studied mechanism and can explain the benefit from GLPs. But I agree, it's not different than a low calorie diet. In the modern times of abundance and sedentary lifestyle, fasting makes wonders. So, if you have even one vascular risk factor, just cut your calories in half, just stop eating. Your body will thank you.