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No-Carb Diets May Impair Memory

Memory Improved When Carbs Reintroduced to Diet
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WebMD Health News

Dec. 12, 2008 - Eliminating carbohydrates from your diet may help you lose weight, but it could leave you fuzzy headed and forgetful, a new study suggests.

One week after starting a weight loss diet that severely restricted carbohydrates, participants in the Tufts University study performed significantly worse on memory tests than participants who followed a low calorie, high-carbohydrate diet.

The low-carb dieters' memory-test performances improved in the following weeks after they began eating some carbohydrates.
"The connection between the foods we eat and how we think doesn't really enter into most people's minds," study co-author and cognitive psychologist Holly A. Taylor, PhD tells WebMD. "But this study demonstrates that the foods we eat can have an immediate impact on brain function."

Carbs Are Brain Fuel

The body breaks carbohydrates into glucose, which it uses to fuel brain activity. Proteins break down into glycogen, which can also be used for fuel by the brain, but not as efficiently as glucose.

So it stands to reason that eliminating carbohydrates from the diet might reduce the brain's source of energy and affect brain function. But there has been little research examining this hypothesis in people following low-carb weight loss diets.

The study by Taylor and colleagues included 19 women between the ages of 22 to 55 who were closely followed after beginning a low-carb weight loss plan similar to the Atkins diet or the low-calorie diet recommended by the American Dietetic Association that includes plenty of fruits, vegetables, and whole grains.

Before starting the diets, the women underwent testing designed to measure long- and short-term memory and attention. The tests were repeated one, two, and three weeks after the diet began.

Low-carb dieters ate virtually no carbohydrates during their first week on the diet. In testing conducted after week one, they performed worse on memory-based tasks than the women following the ADA diet.

Reaction times for those on the low-carb diet were slower and their visual-spatial memories were not as good as the low-calorie dieters.

They did perform better than the low-calorie dieters in testing that measured attention and the ability to stay on task, however.

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