This research, in an upcoming edition of the journal Appetite, found that women who were on a low carb diet had poorer memory function than those on a low calorie diet. Both groups of women lost the same amount of weight over the study period. ( A link to the study is here )
Pound for pound, your brain consumes more energy than any other organ in the body. And your brain lives on glucose - a simple sugar. Yes, your body can make glucose via a process called gluconeogenesis, but it's not enough for your brain, which requires at least one fifth of your daily caloric intake to function properly.
As it turns out, a low carb diet doesn't provide enough carbs for your brain's liking, and memory begins to decline within one week.
Says the press release:
Low- carb dieters showed a gradual decrease on the memory-related tasks compared with the low-calorie dieters. Reaction time for those on the low- carb diet was slower and their visuospatial memory was not as good as those on the low-calorie diet. However, low- carb dieters actually responded better than low-calorie dieters during the attention vigilance task. Researchers note that past studies have shown that diets high in protein or fat can improve a person's attention in the short-term, which is consistent with the results in this study.
Obviously, people with eating disorders (specifically the restrictive types, though people with more bulimic patterns usually have pretty restrictive diets outside any binges) tend to have diets that are low in carbs AND fats AND protein, which makes it really easy to understand why the cognitive effects are so severe. Your brain is affected by malnutrition much more quickly than other organs. Though they soon follow.
And if a run of the mill diet can do this to your brain, imagine what's happening to the brains of those with eating disorders, those on fad diets, those young, growing brains. These memory and cognitive effects happened within one week. Imagine one month...one year...one decade. What then?