In addition to dieting, the participants received guidance about dieting and exercise similar to that offered in commercial weight-loss programs, Foster said.
On average, the participants -- recruited in several cities across the country -- lost 7 percent of their weight after two years, or an average of about just over 15 pounds. The results were similar, no matter which diet they were on.
There was one difference, however. Foster said levels of "good" cholesterol (the heart-healthy kind that you want) grew by about 11 percent in the low-fat group but more than twice that -- about 23 percent -- in the low-carb group. Blood pressure also fell by a greater level in the low-carb group vs. the low-fat cohort.
It's not clear why the low-carb group might perform better in those areas, Foster said, but the two differences are significant. Still, he said, "we can't say following this diet or that diet will result in less heart disease."
Overall, he said, the message of the study is that the diets work about equally well when it comes to weight loss.
Howard Sesso, assistant professor of medicine at Brigham and Women's Hospital in Boston, said this suggests the kind of diet that a person adopts may be less important than his or her ability to stick to it.
There's another message from the study, said Lona Sandon, assistant professor of clinical nutrition at University of Texas Southwestern Medical Center at Dallas. "It confirms what we have known for years: that it's not fat versus carbohydrates. It's the calories that lead to weight loss."
But what of the fact that the participants lost a small percentage of weight, on average? While a small weight loss can make a difference in terms of risk factors for heart disease, "the study shows it is also difficult to take weight off and keep it off long term, even when you have good support," she said. "These people represent what happens in real life
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