Low-fat or low-carbohydrate diets may produce similar weight loss

My patients ask me all the time about the differences between the low-fat diets (i.e., South Beach) and the low-carb diets (i.e., Atkins). In the past, I’ve had little data on which to guide them, but my personal preference has leaned toward the South-Beach-type diets. Now we have some data to help me answer the questions.

USA Today reports that low-fat and low-carbohydrate diets “produce similar weight loss and improvements in many health measures,” according to a study sponsored by the National Institutes of Health and published in the Annals of Internal Medicine.

“To compare the two types of diet plans, researchers at three major medical centers tracked the weight loss of more than 300 obese people for two years. Half of participants followed a low-carb diet, consuming about 20 grams of carbohydrates a day for three months, then gradually increased their carb intake over time,” while the other half “followed a low-calorie, low-fat diet of 1,200 to 1,800 calories a day, depending on their weight and gender, with less than 30% of calories from fat.”

“Both diets improved cholesterol in a two-year study” of 307 adults, the AP reports. However, dieters “on the low-carbohydrate diet got a bigger boost in their so-called good cholesterol, nearly twice as much as those on low-fat.”

Specifically, “the key difference was in HDL, or good cholesterol: a 23 percent increase from low-carb dieting compared to a 12 percent improvement from low-fat, said” the study’s lead author, who likened the improvement to “the kind one might get from medicines that improve HDL.”

The Los Angeles Times “Booster Shots” blog reported that both groups of dieters “also took part in a two-year behavioral program that focused on how to manage relapses, self-monitoring, and an emphasis on moderate physical activity.”

Notably, “after two years, both groups had a 7% weight loss.” Interestingly, the low-carb dieters also “had a substantially greater decrease in diastolic blood pressure … than did the low-fat group at three and six months,” a difference that “still remained after two years.”

According to a MedPage Today story, “Participants in the low-carbohydrate group reported significantly more adverse effects, particularly during the first six to 12 months of the study. The low-carbohydrate diet was associated with more reports of bad breath, hair loss, constipation, and dry mouth.”

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