Quite a lot of research has compared the results of a low-carb diet with a high-carb diet on weight loss. Most of the research shows that low-carb dieters do lose more weight in the short term, (perhaps inspiring people to stay on them), although some studies show that the amount of weight lost over time on the different dietary strategies tends to even out. Later research has investigated other variables besides weight– like triglycerides, HDL cholesterol, blood sugar management and insulin. The vast majority of this research showed that low carb diets perform as well (and in many cases better) than high-carb ones. (Interestingly, no research has shown that low-carb diets are worse, though one might be forgiven for suspecting that in at least some instances, the researchers hoped that would be the case!)
But till now, no one has investigated the impact of low-carb diets on mood and cognition.
In a study just published in the September issue of the American Journal of Clinical Nutrition, researchers from Australia decided to investigate just that. They put 93 overweight or obese men and women on one of two diets- high carb low fat, or low carb high fat. The diets were somewhat calorie restricted and ranged from 1400-1700 calories a day, approximately 30% less than what the participants were used to. The study lasted 8 weeks. At the beginning of the study- and for every 2 weeks afterwards participants were weighed, and also tested on three different standardized assessments of mood. They were also tested on memory and “Speed of cognitive processing”, a measure of how quickly they could perform simple mental tasks.
Here’s what the researchers found. Not surprisingly, the low-carb group lost significantly more weight. But everyone in both diet groups improved in mood, with no significant differences seen between the two groups. Memory was also the same in both groups, and both improved in “speed of cognitive processing” though the low carb group improved slightly less. (The researchers admitted that more studies were needed to see if that minor finding would be replicated.)
We find this study interesting in light of a popular and persistent myth that eating less carbs- especially sugar and processed foods- can make people depressed. This study shows that nothing could be further from the truth. The low carb group improved in mood and overall well-being and lost more weight on top of it -a significant finding from our friends from “down under”.