The low-carb plan included up to 55 percent fat at the beginning, and phased down to about 40 percent. It had about 15 percent carbs initially, and then went to 40 percent. The other dieters followed the American Heart Association's low-fat diet, with no more than 30 percent fat a day.
Both groups had supervised exercise three times a week.
At the meeting, Stewart will report on 46 dieters, 23 from each group, who lost 10 pounds. "In the low-carb group, they reached the 10-pound loss at 45 days," he said. The low-fat group needed 70 days to shed 10 pounds.
Their calorie intake was similar, whichever diet they were on.
Stewart performed the same blood vessel measures as in the breakfast study. "There were no differences in any of the vascular measures," he said.
The researchers will continue the study for six months. While Stewart cautioned that these are initial findings, he added, "We are pretty confident this is a real result. At the 10-pound weight-loss mark, we don't see any harm to the vasculature."
Stewart said he put on weight a few years ago, went on a low-carb plan while also exercising and dropped 40 pounds. He has kept if off for four years.
While the study is intriguing, long-term research is crucial, said Connie Diekman, director of university nutrition at Washington University in St. Louis and past president of the American Dietetic Association.
"When it comes to the impact on blood vessel functioning, as a registered dietitian I would like to see more studies in healthy and unhealthy subjects and longer-duration studies before concluding that this high-fat intake does not impact blood vessel health," she said, although the study does show that exercise is important. The breakfast study, with its one-time test, does not provide much information about what impact these diets
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