This is concerning. Having been placed in a vat of water, a perfectly healthy rat was able to swim to safety every time. The second rat, which has been fed the average American diet—complete with all the fats and sugars Americans regularly consume—doesn't know where to go, exhibiting symptoms typical of a human with Alzheimer's disease. "His brain has been damaged." "These rats were totally normal and then they turned into demented animals." "In this lab, the belief now is that Alzheimer's is really diabetes of the brain, linked to insulin levels, which can be affected by too much sugar."