To Feel Better, Low-Fat Diet May Be Best(izations such as the American Heart Asso...),Health

For the new study, 106 overweight and obese adults, who averaged 50 years old, were randomly assigned to one of two diets -- a low-calorie, low-carb, high-fat plan or a high-carb, low-fat diet -- for one year. Both diets restricted calories to about 1,433 to 1,672 a day.

A year later, average weight loss was about the same in each group: 30.2 pounds.

After the first eight weeks, participants in both groups showed mood improvements, but that lasted only in the low-fat group. After a year, the mood of those in the high-fat group returned to what it had been before they started dieting, the study found.

"The exact mechanism for the observed effects on mood still remains largely unknown," Brinkworth said. "However, if the mechanism for the return of mood toward more negative baseline levels following weight loss with a very low-carbohydrate diet is related to this diet being so far removed from normal dietary habits, then a very low-carbohydrate diet may be best recommended for individuals who habitually consume low amounts of carbohydrate foods in their diet."

More carbs can increase serotonin concentrations in the brain, whereas added fat and protein can reduce concentrations. Serotonin is a neurotransmitter involved in mood.

"Altered mood has been shown to influence interpersonal behavior and, therefore, the consumption of a very low-carbohydrate diet may have psychosocial consequences for interpersonal behavior and relationships," Brinkworth said. "I am not entirely clear as to the effects of mood on long-term weight loss; however a recent review article ... suggested that one of the factors that may pose ri
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