Studies: Structured programs and low-calorie regimens best
By Robin Eisner
MSNBC
NEW YORK, April 8 — Structured weight loss programs allow people to lose more weight over a two-year period than people dieting on their own, a study finds. But for those who want to try to trim their waistlines by themselves, there is no evidence that low-carbohydrate diets, such as the popular Atkins diet, work any better than other regimens, according to another study.
‘More than 30 percent of U.S. adults are now considered obese and although the public has great interest in dieting, Americans still are putting on weight.’
— EDITORS, JOURNAL OF AMERICAN MEDICAL ASSOCIATION
THE TWO STUDIES were among more than a dozen dedicated to obesity that were published in the April 9 issue of the Journal of the American Medical Association. More than 30 percent of U.S. adults are now considered obese and although the public has great interest in dieting, Americans are still putting on weight, JAMA editors said at a press conference describing the studies.
The editors said they focused on obesity and dieting to help educate health care workers and the public about ways to stem the growing obesity epidemic in the United States and provide the best advice available to date about weight loss.
RANDOMIZED TRIAL
In the study of structured weight-loss programs, the researchers performed a rigorous scientific study, called a randomized clinical trial, to compare the effectiveness over a two-year period of a commercial diet program, Weight Watchers, with one where people employed a variety of their own methods to lose weight.
The study, consisting of 65 men and 358 women between 18 and 65 years of age with body mass indices between 27 and 40, was funded by Weight Watchers. (Body mass index is a measure of obesity. Values greater than usually 30 indicate obesity.)
To avoid any possibility of bias, the participants were randomly assigned to either the structured program or the self-help group. Six sites throughout the country were involved in the study.
Subjects in the commercial arm of the study received vouchers to attend Weight Watchers, which offers a dietary program and weight-loss support groups. Nutritionists gave subjects in the self-help study two sessions of counseling about dieting and offered them popular information from books and Web sites.
We wanted to avoid people going on extreme diets, said Dr. Stanley Heshka, associate research scientist in the Institute of Human Nutrition, Columbia University and lead author of the study.
COMMERCIAL PROGRAM BEAT SELF-HELP
After two years, 150 participants (71 percent) in the commercial group and 159 (75 percent) in the self-help group completed the study. The researchers found the self-help group was able to lose and maintain approximately 2.9 to 3.1 pounds for the first year. But during the second year, the self-help group’s weight tended to increase until it returned to baseline, the weight at the beginning of the trial.
In contrast, the commercial group maintained a weight loss of 9.5 to 11 pounds at the end of the first year and was 5.9 to 6.6 pounds lower than baseline weight at the end of the second year.
The individuals who attended more of the Weight Watchers sessions did better than those who attended fewer, Dr. Heshka said.
The authors said their study reports on a particular commercial program with many unique aspects.
“Our results should not be taken as representative of all commercial programs, many of which use other interventions, such as proprietary liquid formulas or diets that are not balanced,” the researchers said.
NO EVIDENCE FOR LOW-CARB BENEFIT
In the other diet study, researchers surveyed medical literature to see if there was any evidence to support the effectiveness of low-carbohydrate diets. The investigators, led by Dr. Dena Bravata of Stanford University in Palo Alto, Calif., found insufficient evidence to make recommendations for or against the use of these diets.
The study, the researchers say, is the first published synthesis of the evidence about such diets from the English medical literature.
Although low-carbohydrate diets have become highly popular among consumers, the American Heart Association and the American Dietetic Association have cautioned against their use. Concerns exist that such diets could have serious medical consequences for people with type II diabetes and high blood pressure.
Bravata and colleagues conducted the search of the medical literature published between 1966 and February 2003 for outpatient studies of adults.
The authors analyzed the data to evaluate changes in weight, serum lipids (cholesterol), fasting serum glucose, fasting serum insulin, and blood pressure.
The authors found 107 articles reporting data on 3,268 participants, of whom 663 received lower-carbohydrate diets (60 grams per day or less of carbohydrates). Only 71 had the lowest-carbohydrate diets — 20 g/d or less of carbohydrates (the recommended threshold for some of the most popular diets).
No study evaluated diets of 60 g/d or less of carbohydrates in participants with an average age of 53 years or older, Bravata said. Only five studies evaluated these diets for more than 90 days.
NO MAJOR HEALTH RISKS FOUND
Among obese patients, weight loss was associated with longer diet duration and restricted calorie intake, but not with reduced carbohydrate content, the researchers found.
Yet, they also found that low-carbohydrate diets had no significant adverse effect on serum lipid, fasting serum glucose, fasting serum insulin levels or blood pressure.
Bravata said the findings show that insufficient evidence exists to determine the effectiveness of low-carbohydrate diets, but if individuals have lost weight on them and want to use them for a period longer than 90 days, she recommends that doctors monitor the dieter’s health.
In response to the JAMA study, the Atkins Health and Medical Information Services, of New York City, said the report did not include more recent data from newer and longer studies that show weight-loss and disease prevention benefits unique to diets low in carbohydrates.
To help fill in the gaps in the current medical knowledge about low-carbohydrate diets, a federally-sponsored study is beginning to examine the effectiveness of the Atkins diet.
