Monday, November 09, 2009

Low-Fat Diet Makes People Less Angry Than Low-Carb, Study Says

By Simeon Bennett

Nov. 10 (Bloomberg) -- Dieters eating food high in carbohydrates and low on fat improved their mood longer than those on a low-carb, high-fat regime similar to the Atkins diet, researchers say.

A study of 106 overweight or obese people in Australia found those on the low-fat diet, which included bread, pasta and rice, were less angry, depressed and confused after one year than those who ate fewer carbs and more meat and dairy products, according to the study published today in the journal Archives of Internal Medicine. Both diets were equally effective at reducing weight, the research showed.

More than 72 million Americans, or one-third of U.S. adults, are obese, according to the U.S. Centers for Disease Control and Prevention. The findings by researchers from Australia’s Commonwealth Scientific and Industrial Research Organisation contradict earlier, smaller studies that showed no mood changes in people linked to different diets. More research is needed to explain the differences, they said.

“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,” scientists led by Grant Brinkworth said in the latest study.

Both diets contained the same amount of energy in terms of kilocalories. Participants in the high-carb, low-fat diet got their energy from foods with 10 times the carbohydrates, half the fat and less protein than those on the low-carb, high-fat diet, the researchers said.

30 Pounds Lighter

The average weight loss for participants was 13.7 kilograms (30.2 pounds), with no significant difference between the two groups. The participants had an average body mass index, defined as weight in kilograms divided by height in meters squared, of 33.7 when the study began. An adult is considered overweight with a BMI of more than 25, and obese if the BMI is 30 or greater, according to the CDC.

The researchers also found that both diet groups showed similar improvement in memory and no significant change in speed of mental processing.

An earlier analysis found both groups were less angry, depressed and confused after eight weeks of dieting than when they started. Over the course of a year, those on the low-fat diet maintained their improved mood, while those on the low-carb plan moved back toward levels at the start of the study, Brinkworth and colleagues said.

One possible explanation for the difference is that eliminating carbohydrates is such a dramatic change to the typical Western diet that volunteers may have suffered withdrawal symptoms over time, the authors said. Further studies are needed to validate that hypothesis, they said.

The study was funded by Australia’s National Heart Foundation, the National Health and Medical Research Council, and four closely held Australian food companies, including nut growers.

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