Healthy living * Weight loss

High carb, low fat diet boosts mood

Zone default image Low carb diets have no effect, study finds

A diet high in carbohydrates and low in fats not only helps you lose weight, but also has the added benefit of boosting your mood a year later, new research suggests.

By contrast, a diet which is low in carbohydrates but high in fats, such as the Atkins diet, may help with weight loss, but has no effect on a dieter's mood.

Australian scientists compared both types of diet to find out how they affected the dieter's long term mental health. Although people who are obese often report an improvement in mood when they start losing weight, the effect usually wears off quickly.

"The obesity epidemic has led to widespread interest in alternative dietary patterns for weight management, including very low-carbohydrate 'ketogenic' diets that are typically high in protein and fat (particularly saturated fat)," the research said.

"While recent clinical studies have shown that low-carbohydrate diets can be an effective alternative dietary approach for weight loss, their long-term effects on psychological function, including mood and cognition, have been poorly studied".

In the study, conducted by the Commonwealth Scientific and Industrial Research Organisation, 106 overweight and obese people with an average age of 50 were put on a either a very low carbohydrate diet, high fat diet or a high carbohydrate, low fat diet for one year. Both diets had the same number of calories.

Changes in body weight, mood and well-being, thinking, learning and memory skills were recorded through the year.

The results, published in the journal Archives of Internal Medicine, found that both sets of dieters lost an average of 30.2 pounds.

When it came to mood, both groups reported an improvement after 8 weeks, but after a year this was only found in the dieters on the high carbohydrate, low fat diet. The mood of people on the high fat, low carbohydrate regime returned to what it had been at the start of the diet.

As to how the high fat, low carbohydrate diet affects a persons mood, scientists suggested it may be linked to serotonin levels in the brain. Past studies have linked low serotonin levels to changes in mood and it's already known that increases in fat and protein can cause levels to fall. But the exact mechanism remains unknown.

However, the health benefits gained by losing weight on the low carbohydrate, high fat diet may not outweigh the negative effect the diet had on mental well being, said the researchers.

There was no evidence that either diet was associated with changes in mental processing, since 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 scientists concluded.

This article was published on Tue 10 November 2009

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