Low Carbs: The Adventure Continues

The headline "Study Bolsters Low-Carb Diet" captured some attention last week from both scientists and Lean Plate Club members. The news reports about the study, presented by a team of scientists from the Harvard School of Public Health at an annual meeting of obesity researchers, suggested a dieter's dream: low-carbohydrate eaters could consume more calories -- 300 calories additional per day than low-fat dieters -- and lose the same amount of weight.

That's provocative stuff, suggesting that something about the low-carb diet could be speeding up metabolism. It caused some neck-snapping in the nutrition community. But even the authors of the study urged caution. "It was small and preliminary," notes the study's co-cauthor Walter Willett, chair of nutrition at the Harvard. "The basic conclusion is that this issue needs to be studied further."

Here are more details about the findings from Penelope Greene, a visiting scholar at Harvard and the statistician who led the study, as well as other weight loss experts who attended the North American Association for the Study of Obesity meeting last week in Fort Lauderdale, Fla.

First, a few basics Greene and colleagues recruited 21 adults age 50 and older. They had an average body mass of 33, placing them in the obese category. All had tried to lose weight before. Some took medication to control high blood pressure, others for reducing cholesterol levels. Some of the women were on hormone replacement therapy. But generally, all participants were in good health.

The deal Volunteers agreed to eat only the food provided by the study for the next 12 weeks. All meals were cooked and packaged by a restaurant in Cambridge, Mass., using recipes supplied by Greene. Food was picked up each day by participants from Greene. Participants also agreed to keep their level of physical activity constant during the 12-week study. They underwent periodic blood and urine testing during the study.

The plan Subjects were randomly assigned by Greene to one of three groups. Two groups of seven people each ate the same number of calories: 1,500 per day for women; 1,800 for men. One group followed a low-fat, American Heart Association regimen with about 30 percent of calories from fat. A second group ate the same number of daily calories using a low-carbohydrate regimen advocated by the late physician Robert Atkins. A third group also received low-carb meals, but were given an additional 300 calories per day. All three groups returned any leftovers to Greene the following day for weighing.

The sponsor The Robert Atkins Foundation. Greene says she proposed the study to the foundation, which had no input into the study's design or results.

Findings While members of the low-carb groups lost more weight on average, the differences were not statistically significant. Overall, the groups shed about 11/2 to 2 pounds per week, considered a safe rate of weight loss. Specifically:

• The low-fat group lost 17 pounds in 12 weeks, or eight percent of body weight. Members trimmed about three inches from their waists and two inches from their hips.

• The low-carbohydrate group (eating the same number of calories as the low-fat group) lost 23 pounds, about 11 percent of their body weight. Waistlines in this group shrunk by four inches and hips by three inches.

• The higher-calorie low-carbohydrate group lost 20 pounds, or roughly 10 percent of their body weight. They dropped four inches from their waistlines and three inches from their hips.

Perspective. Greene cautions that this is a small study not intended to answer major questions. But she notes that her findings suggest that the third group ate 25,000 more calories and lost the same amount of weight as the other two groups. Taking that into account, Greene says, would make the results "statistically significant." Greene isn't sure what accounts for the findings. One explanation: "Some of those extra calories [eaten by the low-carb dieters] may have been excreted," she says.

What some experts say Several researchers pointed out that the study is not yet published or peer-reviewed, and that they have not seen the details, making it difficult to determine its significance. "But let's assume [for purposes of discussion] that it was the most carefully controlled, well-conducted study," says Gary Foster, author of a study on the Atkins diet that was published in May in the New England Journal of Medicine. (His study found that the low-carbohydrate regimen produced a greater weight loss at six months than the low-fat approach but that at one year, the weight loss was not statistically different.) "It's intriguing and would be sort of counter to everything we know," in that it would suggest a greater calorie intake can result in greater weight loss. "So it's appropriate to be skeptical at this point."

Arthur Frank, director of the George Washington University Weight Management Program, says the conclusions that those in the third group had increased metabolism, perhaps accounting for their being able to eat more calories without gaining weight, "are not justified by the data."

The study "raises some interesting questions," says James Hill, director of the Clinical Nutrition Research Unit at the University of Colorado Health Sciences Center in Denver. Consumers and experts, he says, "keep looking for magic ways of weight loss, whether it's Atkins or Ornish. But we are eating too much of everything. We have to cut down on calories and portion sizes and passive overeating." Plus, Hill says, increasing physical activity is essential. Otherwise, studies suggest that efforts at maintaining weight loss "will be in vain."

-- Sally Squires

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