Cognitive decline that often accompanies obesity and diabetes can be reversed with regular exercise or surgical removal of belly fat, scientists report. A drug already used to treat rheumatoid arthritis also helps obese/diabetic adult mice regain their ability to learn and comprehend, while transplanting belly fat to a normal mouse reduces those abilities. Studies in humans and animals indicate that obesity and diabetes -- which often go hand in hand -- essentially triple the risk of mild cognitive impairment as well as Alzheimer's.