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Study Shows Low-Fat Diets Produce Better Mood Than Low-Carb

By L. K. Regan

Thanksgiving has been and gone, and all that's left is a pile of turkey sandwiches. After we snarf those down, it might be time to think about the post-holiday weight-loss plan. Which way to go, low-fat or low-carb? Well, a new study suggests that if you want to keep the holiday spirit going year-round, a low-fat diet is much better for your mood than cutting the carbs.

The Australian study, appearing in this month's Archives of Internal Medicine, spent a year following 106 overweight and obese people who were randomly assigned to one of two diets: either a low-carb, high fat diet, or a high-carb, low-fat diet. Both groups lost the same average amount of weight—just over 30 pounds—and both at first reported a boost in mood. This was consistent with research that losing weight by any means will lead to an improvement in a person's psychological state. But the joie de vivre was short-lived in one of the groups: the low-carb dieters returned to their slightly negative mood baseline by the end of the year.

The researchers were tracking a variety of cognitive measures in the course of the study: mood, sense of well-being, memory skills, learning skills, etc. But only mood was susceptible to dietary differences within the study. "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," the authors write. "Further studies are required to evaluate the effects of these diets on a wider range of cognitive domains."

Why is mood so vulnerable to differences between types of diets? Researchers offer a range of possible explanations, from the social problems that arise from trying to avoid carb-heavy Western food (constantly saying no to pizza, pasta, and bread gets tiring and attracts negative comments), to the potential effects of fats and protein on serotonin, a neurotransmitter that can regulate mood. More research will be needed to reach a definitive conclusion, but in the meantime, unless you want to be a Grinch long past Christmas, a post-Thanksgiving diet might be better off with less Turkey than stuffing.