Can a Very Low-Carbohydrate Diet And a Low-Fat Diet Affect Mood and Cognitive Function?

Long-term Effects of a Very Low-Carbohydrate Diet and a Low-Fat Diet on Mood and Cognitive Function

Despite official recommendations advocating high carbohydrate low fat diets, very low carbohydrate high fat diets have gained a lot of popularity for weight reduction.  They may be effective in managing weight, but, the long term effects of these low carbohydrate diets on cognition and mood are still not very clear.

Grant D. Brinkworth, Ph.D., of Commonwealth Scientific and Industrial Research Organization-Food and Nutritional Sciences, Adelaide, Australia, and colleagues conducted a randomized clinical trial to study this phenomenon.

An earlier small 4-week study on obese women showed reduced cognitive function as a result of consumption of a very low-energy, low carbohydrate ketogenic diet compared to a higher-carbohydrate, lower-fat diet.  Another 3 week study of overweight and obese women showed poorer memory function, but improved performance on a vigilance-attention task when put on a low calorie low carbohydrate diet compared with a low fat diet.

But these studies and some others were somewhat preliminary. Thus, a long term study was undertaken to observe changes in body weight, psychological mood, well-being and cognitive functioning. The report was published in the November 9 issue of Archives of Internal Medicine. 106 overweight and obese individuals with a mean average age of 50 years and BMI of 33.7 participated in the study. They were randomly assigned to 2 groups. One group consisting of 55 participants received energy restricted isocaloric very low carbohydrate, high fat diets for 1 year. The other group with 51 participants was given a high carbohydrate, low fat diet for the same period of time. Changes in body weight, cognitive functioning and mood were studied periodically during the 1 year period.

At the end of the year, the overall mean average weight loss was 13.7 kg with no significant differences between groups. Both groups initially showed improvement in mood. But these positive changes were sustained only in the low fat group. The other group came back to their original state.

"This outcome suggests that some aspects of the low-carbohydrate diet may have had detrimental effects on mood that, over the term of one year, negated any positive effects of weight loss," the authors write.

Both groups experienced similar changes in thinking and memory performance over time.
"Further studies are required to evaluate the effects of these diets on a wider range of cognitive domains," the authors conclude.

By. Poonam Vaswani,
Dietitian Online,
NutritionVista.com