Researchers at Tufts University have seen results that may indicate that a low-carb diet, such as the popular Atkins Diet, reduces the ability to learn, think, and remember. I'm not kidding -- here is a LINK to a summary of their findings which report that severe carbohydate reductions reduce the amount of glucose that is the brain's primary energy source. Testing college students revealed a drop in cognition during the dieting, and a recovery after cessation of the diet.