Researchers from the Tufts University Department of Psychology, led by professor Holly A. Taylor, have just revealed the results of the studies they recently carried out, pointing to the consequences that a low-fat dieting plan might have on the brain activity. Their conclusions, summed up in a study called “Low-carbohydrate weight-loss diets. Effects on cognition and mood,” will be published in the February 2009 issue of the “Appetite” journal.

The group of scientists believes that the poor intake of low-carbohydrates can affect one's mood and cognition in a negative way, as a direct result of the fact that the brain uses, as its basic “energy supplier,” the glucose coming from food. If one's diet lacks such nutrients, the brain's activity will undergo important changes.

To see just how accurate their suppositions were, the researchers selected a group of 19 women, aged from 22 to 55 years old, and asked them to choose either a low-fat diet or a low-calorie weight-loss plan, especially created by the American Dietetic Association. Nine of the participants preferred the first option, while the rest went for the latter.

All the women carried out various tests, in five distinct sessions, screening special cognitive skills, such as attention (including the visual type), spatial memory, long-term and short-term memory. The scientists first supervised the women’s reactions to various stimuli before the beginning of the dieting period, and then twice in the first week. The last two screenings were made when the diet was over and the subjects went back to their regular eating habits.

When testing was over, Dr. Taylor concluded that, “The data suggest that after a week of severe carbohydrate restriction, memory performance, particularly on difficult tasks, is impaired.” All the women in the low-carb diet group consequently needed more time to respond to certain stimuli than those following the low-calorie weight-loss plan, while their visuospatial memory was also affected. Researchers also had the chance to reinforce what previous studies had already concluded, when observing that the same low-fat dieters had, paradoxically, better reactions to the tests scanning the short-term vigilance skills.