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Health & Balance

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Diet Moodiness: Low-Fat vs. Low-Carb

Study Shows Initial Weight Loss Boosts Mood on Both Diets but Didn't Last on Low-Carb Diet
WebMD Health News
Reviewed by Louise Chang, MD

Nov. 9, 2009 -- If you're looking to lose extra pounds and weighing the options of a low-fat diet vs. a low-carbohydrate diet, you might want to consider the moody findings of a new diet study.

The study, published in the Archives of Internal Medicine, shows a short-term improvement in the moods of people who went on low-fat and low-carb diets.

But those mood gains didn't last in the long run for people on low-carb diets.

The study included 106 overweight and obese adults (average age: 50) in Adelaide, Australia. They were randomly split into two groups. One group was assigned to go on a low-fat diet for a year. The other group was assigned to go on a low-carbohydrate diet for a year.

Here's a quick look at those two diets:

Low-fat diet: 46% of calories from carbohydrates, 24% of calories from protein, and 30% of calories from fat (less than 8% from saturated fat).

Low-carb diet: 4% of calories from carbohydrates, 35% of calories from protein, and 61% of calories from fat.

People in both groups got the same daily calorie budget. They also met regularly with a dietitian and completed mood surveys several times during the yearlong study.

By the end of that year, people in both groups had lost the same amount of weight -- about 30 pounds.

At first, mood improved for people in both groups. That was no surprise; the researchers had expected to see that bounce in mood as people started to shed extra pounds.

But better moods didn't last for people on the low-carb diet. By year's end, their mood was right back where it had been before dieting and losing weight.

However, the mood improvements lasted for people on the low-fat diet.

It's not clear why the mood benefits faded for people in the low-carb group.

But the researchers suggest that the low-carbohydrate diet may have been too hard and too different from how people used to eat.

The low-carb diet may have been "so far removed" from normal eating patterns that it became a lot of work and a social burden, note the researchers, who included Grant Brinkworth, PhD, of the Commonwealth Scientific and Industrial Research Organization in Adelaide, Australia.

"Although, in the short term, participants may have been able to meet the challenges presented by this dietary pattern, over the longer term, it may have increased participant isolation, leading to the negative impact on mood state that may provide a possible explanation for the effects that were observed," Brinkworth and colleagues write.

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