Major diets give similar test results
By Sally Squires The Washington Post Posted November 16, 2003
No difference in pounds lost. That was the conclusion of the first long-term, head-to head trial of four well-known diets: Atkins, Ornish, Weight Watchers and the Zone. Conducted by researchers at Tufts University, the findings were released recently at the American Heart Association's annual meeting in Orlando.
In the year-long study, 160 overweight and obese people were randomly assigned to one of these four regimens. Those in the Atkins, Zone and Ornish programs received a book describing their eating plans. The Weight Watchers group got a cookbook published by Weight Watchers International. (This difference has drawn criticism from Weight Watchers because the organization's full program is not outlined in any book.)
All participants were generally healthy, but had at least one additional major risk factor for heart disease, such as high blood pressure, elevated blood cholesterol, increased blood sugar levels or diabetes.
Food-consumption records were collected throughout the study. Blood and urine were also analyzed so that researchers could assess heart disease risk.
The good news: All the diets seemed safe and all produced weight loss, although there were no huge drops in poundage. All programs also reduced participants' risk of heart disease to a statistically significant degree.
"The study shows that no single approach has a monopoly on weight loss," says Thomas Wadden, director of the University of Pennsylvania's Weight and Eating Disorders Program.
OK, so what are the take-home messages?
Expect no miracles. On average, the programs produced a weight loss of 2 percent to 3 percent, or four to six pounds for a 200-pound person.
Stay the course. Not surprisingly, people who stuck with the regimens for the full year dropped the most pounds. The Atkins, Weight Watchers and Zone participants who completed the program lost 4 percent to 5 percent of their body weight. People who stayed the course with Ornish lost about 6 percent. "Unfortunately for each diet, the adherence gradually waned over time," says Michael Dansinger, director of Obesity Research at the Tufts New England Medical Center's Atherosclerosis Research Lab and lead author of the study.
Moderate changes seem easier to maintain. About half the people following Atkins and Ornish, which have more dietary restrictions than the other programs, dropped out before the study ended. By comparison, about two-thirds of those on the Weight Watchers and Zone regimens completed the study, although these differences were not statistically significant.
A healthy high-carbohydrate diet does not appear to raise insulin levels. That's been a worry about very high carbohydrate approaches like that developed by California cardiologist Dean Ornish. Critics have suggested that they could raise the risk of diabetes by overtaxing production of insulin, the hormone that regulates blood sugar levels. But the study found that at 12 months, people in the Ornish group experienced a 27 percent reduction in insulin levels.
All four regimens reduced heart-disease risk. The biggest reduction was in the Weight Watchers group (15 percent), followed by Atkins (12 percent), the Zone (11 percent) and Ornish (7 percent). The Atkins approach has been criticized for potentially raising cholesterol levels. But this study, like others published earlier this year, found no significant differences in total cholesterol or levels of low-density lipoprotein (the most damaging form of cholesterol) among Atkins dieters.
Figure out what works best for you. All the programs resulted in weight loss.
"The moral of the story is: Find the diet you can stick to," Dansinger says. "This idea of a one best diet for everyone is probably an old-fashioned notion."