While weight loss is associated with improved mood and sense of well-being in those who are overweight or obese, the process of dieting can alter chemicals in the brain that regulate mood and brain function.  Grant D. Brinkworth, from Commonwealth Scientific and Industrial Research Organization Food and Nutritional Sciences (Australia), and colleagues studied 106 overweight and obese men and women, who were randomly assigned to an energy-restricted diet that provided 1,433 to 1,672 kcal through one of two strategies: as either a low-fat, high-carbohydrate diet comprised of 46% of total energy from carbohydrates, 24% from protein, and 30% from total fat (less than 8% saturated fat); or a low-carbohydrate, high-fat diet with the goal of 4% of total energy from carbohydrates, 35% from protein, and 61% from fat (20% saturated fat).  While both groups achieved substantial weight loss over one year, averaging 13.7 kg (30.2 pounds) without a difference between groups , with similar changes in glucose and insulin levels, and improvements in mood and well-being, over the course of time the mood scores rebounded in the low-carb group.  At one-year post-study, reassessment showed significantly better scores for the low-fat diet, as compared with low-carb diet, for parameters of anger and hostility, confusion and bewilderment, and depression and dejection, as well as overall mood.  Write the researchers: “ Over 1 year, there was a favorable effect of an energy-restricted [low-fat] diet compared with an isocaloric [low-carb] diet on mood state and affect in overweight and obese individuals. Both diets had similar effects on working memory and speed of processing.”