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c.1996 Medical Tribune News Service

WASHINGTON - Low-carbohydrate, high-protein diets may be self-defeating - and bad for your psychological health as well, new research suggests.

The reason: people who eat low-carbohydrate, high-protein diets to lose weight often become tense or depressed, and end up turning to carbohydrate-rich fatty snacks, a Boston researcher reported here Monday.

Low-carbohydrate foods trigger a change in behavior through a chain of chemical events in the brain: the reduced absorption of the amino acid tryptophan into brain cells decreases the levels of serotonin, a chemical that affects mood, reported Judith J. Wurtman, head of the Nutrition and Behavior Studies Group at the Massachusetts Institute of Technology Clinical Research Center in Boston.

Low serotonin levels, in turn, cause people to feel irritable, anxious and depressed, which causes them to crave high-carbohydrate foods, Wurtman reported here Monday at a conference on obesity.

On the other hand, diets that are high in carbohydrates and low in protein help increase brain serotonin levels, thus helping to improve mood and appetite, she said.

Low-carbohydrate, high protein formulations are the basis of many commercial liquid diets, she noted.

In an ongoing study of 40 obese women who had a long history of diet failure due to stress-related overeating, Wurtman found that those who consumed a 1,400-calorie, high-carbohydrate, low-protein diet reported significantly fewer cravings and better overall moods after seven weeks than those who followed a high-protein, low-carbohydrate diet totaling 1,400 calories.

The women on the high-carbohydrate diet also lost significantly more weight by the end of the study than the high-protein diet group, she said. The high-carbohydrate group lost two to nine pounds, whereas the other group either lost fewer than two pounds or actually gained weight because they indulged in high-carbohydrate snacks.

``Since tryptophan uptake in the brain is associated with the synthesis and release of brain serotonin, and since serotonin regulates both carbohydrate appetite and mood, this dietary intervention may be useful in controlling stress-generated overeating,'' she said.

A better understanding of what causes overeating is necessary to solve the obesity problem in the United States, where 30 percent of the population is overweight, Wurtman said.

About 99 percent of people who complete a weight-loss plan in this country gain their weight back within five years, she said, adding that low levels of carbohydrates in many weight-loss regimens may explain this widespread failure.

Women who experience premenstrual syndrome and people with seasonal affective disorder - conditions that share mood states with stress-related overeating - also often crave carbohydrates, according to Wurtman. ``The consumption of carbohydrate-rich food is an attempt by such people to make themselves feel better,'' she said.

But when people crave carbohydrate-rich foods, they probably also crave high-fat foods, said Patrick M. O'Neil, director of the Weight Management Center and professor of psychiatry and behavioral sciences at the Medical University of South Carolina in Charleston.

Otherwise, they would crave fruits and bland carbohydrate-rich foods, rather than chocolates and sweets, he said.

So the role carbohydrates play in weight control may be ``overstated,'' O'Neil said. A pleasant tasting food also can make people feel better, he said.

In addition, most people who are dieting do not report dieting-induced depression or other mood swings, he said.

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