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Dieting Affects Mood and Brain Function

Original Source: http://www.worldhealth.net
Original Publication Date: November 11, 2009

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.”

Background Very low-carbohydrate (LC) diets are often used to promote weight loss, but the long-term effects on psychological function remain unknown.

Methods A total of 106 overweight and obese participants (mean [SE] age, 50.0 [0.8] years; mean [SE] body mass index [calculated as weight in kilograms divided by height in meters squared], 33.7 [0.4]) were randomly assigned either to an energy-restricted (approximately 1433-1672 kcal [to convert to kilojoules, multiply by 4.186]), planned isocaloric, very low-carbohydrate, high-fat (LC) diet or to a high-carbohydrate, low-fat (LF) diet for 1 year. Changes in body weight, psychological mood and well-being (Profile of Mood States, Beck Depression Inventory, and Spielberger State Anxiety Inventory scores), and cognitive functioning (working memory and speed of processing) were assessed.

Results By 1 year, the overall mean (SE) weight loss was 13.7 (1.8) kg, with no significant difference between groups (P = .26). Over the course of the study, there were significant time x diet interactions for Spielberger State Anxiety Inventory, Beck Depression Inventory, and Profile of Mood States scores for total mood disturbance, anger-hostility, confusion-bewilderment, and depression-dejection (P < .05) as a result of greater improvements in these psychological mood states for the LF diet compared with the LC diet. Working memory improved by 1 year (P < .001 for time), but speed of processing remained largely unchanged, with no effect of diet composition on either cognitive domain.

Conclusions Over 1 year, there was a favorable effect of an energy-restricted LF diet compared with an isocaloric LC diet on mood state and affect in overweight and obese individuals. Both diets had similar effects on working memory and speed of processing.

Trial Registration anzctr.org.au Identifier: 12606000203550

Author Affiliations: Preventative Health National Research Flagship, Commonwealth Scientific and Industrial Research Organisation–Food and Nutritional Sciences (Drs Brinkworth, Noakes, Clifton, and Wilson), Nutritional Physiology Research Centre, Samson Institute for Health Research, University of South Australia (Dr Buckley), and Flinders Centre for Cancer Prevention and Control, School of Medicine, Flinders University (Dr Wilson), Adelaide, Australia.

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