A three center study led by researchers at the Weight and Eating Disorders Program of the University of Pennsylvania School of Medicine reports the results of the first of two new controlled trials of the Atkins Diet.
Compared to a conventional, high carbohydrate, low-calorie approach, the Atkins Diet limits carbohydrates but permits unrestricted amounts of protein and fat. In the first study published in the May 22 issue of the New England Journal of Medicine, Atkins dieters lost twice as much weight at 3 and 6 months but there was no difference between the groups at 1 year. Despite the lack of differences in weight loss at 1 year, the Atkins dieters had significantly greater increases in good cholesterol (HDL) and greater decreases in triglycerides.
Led by Gary Foster, Ph.D. Associate Professor of Psychiatry and Clinical Director of the Weight and Eating Disorders Program at the University of Pennsylvania, the study investigated 63 obese men and women who were 44 years of age and weighed and average of 216 pounds.
All participants met with a registered dietitian at 0, 3, 6 and 12 months. Those in the Atkins group were given a copy of Dr. Atkins New Diet Revolution and asked to follow the diet as described. The conventional diet group was given instructional materials on a 1200-1500 calories/day (women) or 1500-1800 calories /day (men) diet that consisted of 60% carbohydrate 25% fat, and 15% protein based on the Food Guide Pyramid.
Results showed the Atkins participants lost an average of 14.7 pounds compared with 5.8 pounds in the conventional group at 3 months, 15.2 pounds versus 6.9 pounds at 6 months, and 9.5 versus 5.4 pounds at 12 months. At 1 year, Atkins participants had greater increases in HDL cholesterol (18% vs. 3%) and greater reductions in triglycerides (-28% vs. 1%) than did those following a conventional diet. Neither group showed changes in LDL (bad) cholesterol at 1 year.
“Obesity is a national public health problem, and we need to evaluate alternative weight loss approaches aggressively. Widely recommend low carbohydrate approaches may be premature, but our initial findings suggest that such diets may not have the adverse effects that were anticipated” Foster stated. “The real issue is whether low carbohydrate approaches help patients maintain their weight loss better than conventional approaches. It will also be important to determine whether the effects of the diet on cholesterol are the same during weight maintenance as they are they are during weight loss.” Foster also cautioned.
Results of this first, randomized, controlled study of the Atkins diet suggest that low- carbohydrate diets may not be as harmful as anticipated. “Larger and longer studies are needed to assess the long-term safety and efficacy of low carbohydrate approaches in the management of obesity. These preliminary data suggest that weight losses will be comparable to conventional approaches over a 1 year period, but there may be some favorable effects of a low-carbohydrate approach in terms of triglycerides and HDL (good) cholesterol,” Foster said.
Low-carb outperforms low-fat in VA study
In the second study also published in the May 22 New England Journal of Medicine showed obese patients on a low-carbohydrate diet for six months lost more weight and fared better on certain cardiovascular and diabetes measures than patients on a low-fat, calorie-restricted diet, according to the Department of Veterans Affairs (VA).
Lead author Frederick F. Samaha, M.D., chief of cardiology at the Philadelphia VA Medical Center and assistant professor at the University of Pennsylvania School of Medicine (UPSM), cautioned against discarding the low-fat approach, which has been shown to cut the risk of heart attack, but he also said more attention needs to be paid to the harmful effects on body chemistry of carbohydrate-rich diets. “There are important metabolic effects to a high-carbohydrate diet in a person who tends to overeat, and we need to take a close look at that,” said Samaha.
Linda Stern, M.D., co-leader of the study, said the research is among the first clinical trials of a low-carbohydrate diet in a population other than healthy volunteers. The study volunteers were severely obese–their average weight was 288 pounds–and many had conditions such as diabetes, heart disease, hypertension, high cholesterol and depression.
“Our results may be surprising to some people,” said Stern, a primary care doctor with VA and clinical assistant professor of medicine at UPSM. “Diabetics in particular did very well on the low-carbohydrate diet. So, especially in the realm of lifestyle modification, we might have to broaden our horizons on what we’re recommending.”
In the study, 132 men and women were randomly put on either a low-fat or low-carbohydrate diet for six months. The low-carbohydrate group was told to limit carbohydrate intake to 30 grams per day. They received counseling on healthy types of fat, such as omega-3 fatty acids, but had no limit on total fat intake. The low-fat group was put on a calorie-restricted diet, with no more than 30 percent of total caloric intake from fat.
Overall, volunteers assigned to a low-carbohydrate diet lost an average of about thirteen pounds, compared to four pounds for the low-fat group. The low-carbohydrate dieters reduced their levels of triglycerides–blood fats that, like cholesterol, may contribute to clogged arteries–by an average of 20 percent, versus four percent for the low-fat group. There were no significant changes in cholesterol or blood pressure levels in either group.
The authors said the study results underscore the paradox of America’s fascination with low-fat eating: Americans are taking in less fat, but not losing weight or improving their cardiovascular health as a result.
“People have gotten the message loud and clear–they’re restricting their fat,” said Samaha. “But they’re still overeating. And when they overeat carbohydrates, they remain overweight and perhaps even exacerbate the development and management of diabetes, unfavorable lipids and heart disease.”
Among non-diabetic people in the study, insulin sensitivity improved for the low-carbohydrate group, but worsened somewhat for the low-fat group, possibly raising their risk of diabetes. Among diabetic participants, the low-carbohydrate dieters reduced their fasting blood-sugar levels by about nine percent, versus only two percent for the low-fat dieters. Over the six-month study, seven diabetic patients in the low-carbohydrate group were able to reduce their dose of insulin or other medication to control blood sugar. In the low-fat group, one diabetic patient lowered his insulin dose and one had to begin therapy.
Samaha pointed out that even though all the study participants remained extremely overweight, those in the low-carbohydrate group significantly reduced risk factors for diabetes and heart disease: Their triglycerides dropped to normal range, and their glycemic, or blood sugar, levels approached normal. “The metabolic effects were fairly impressive,” said Samaha.
The study provides some validation for the eating plan advocated by the late Dr. Robert Atkins, the well-known diet doctor who died last month. Atkins advised patients to cut down on carbohydrates, especially refined carbohydrates, and not to worry about saturated fat–butter, cream, steak–as long as they were limiting carbohydrates.
According to Stern, eating fewer carbohydrates and more protein and fat makes people feel fuller and less likely to consume extra calories. It avoids blood sugar fluctuations and the constant insulin spikes that lead to the development of insulin resistance, which sets the stage for diabetes.
Said Samaha: “There are aspects of what Dr. Atkins was saying that were not being taken seriously, and perhaps should have been. There are important risks in over-consuming carbohydrates.”
A review article in the April 9 Journal of the American Medical Association, analyzing scores of studies from the past three decades, concluded there was not enough evidence to recommend for or against low-carbohydrate diets. Samaha asserted most of the studies looked at were too small to produce meaningful data, or did not compare the diet to a traditional low-fat diet. He said studies with more participants, over longer periods of time, are needed to gauge the true effects of low-carbohydrate versus low-fat eating, especially on the risk of heart attack.
The ideal approach, said the authors, may be to focus less on the proportions of fat and carbohydrate in the diet and more on the quality of foods. One reason for the apparent failure of low-fat diets, they said, is that people tend to make up for lower fat intake by eating more junk food. “People shouldn’t get the message that as long they lower their fat intake they can eat all kinds of carbohydrates–candy, cookies, sugar-coated cereals, and other foods that may not be that healthful,” said Samaha. He cited vegetables with a high fiber-to-carbohydrate ratio as an example of the “good” carbohydrates that should play a greater role in either low-fat or low-carbohydrate eating plans.
Stern pointed out that even the best diet must be combined with other lifestyle changes, such as increased physical activity, to combat obesity. “Half the equation is to get people to be aware of what they’re eating, and to eat less,” she said. “The other half is to get them to move. Any weight loss program, at the VA or elsewhere, must include a formal exercise program.”
No Magic Bullet to Safe and Healthful Weight Loss
According to the American Dietetic Association (ADA) the results these new studies support their position that the most effective method of healthy lifelong weight management includes an eating plan that is based on complex carbohydrates such as whole grains, fruits and vegetables, moderate in protein and relatively low in fat, coupled with daily physical activity.
The studies look at the effectiveness of “carbohydrate-restricted” diets over six months and low-carb, high-protein, high-fat approaches such as the Atkins Diet over three, six and 12 months.
“The findings confirm what we already know,” said registered dietitian and American Dietetic Association spokesperson Kathleen Zelman. “There is no magic bullet to safe and healthful weight loss.”
Zelman added: “In the short term, these studies show you can achieve weight loss with low-carb diets. But in the long term, success rates were not different from people who are on a more ‘traditional’ diet. These results don’t change ADA’s recommendations for achieving healthful weight that can be sustained over a lifetime.”
ADA’s advice is based on the National Academy of Sciences’ recommendations that adults obtain 45 percent to 65 percent of their calories from carbohydrates, 20 percent to 35 percent from fat and 10 percent to 35 percent from protein.
“These recommendations provide you with a good deal of room to increase your level of protein, which other recent studies have suggested can be effective, without going to the level of the Atkins Diet,” Zelman said. “You can move toward the higher end of the protein range, stay at the lower end of the fat range and make sure your carbohydrates are complex, meaning whole grains such as whole wheat pasta.”
Registered dietitian and ADA spokesperson Keith Ayoob noted that many people in the studies apparently had trouble staying with the low-carbohydrate diet and there were many dropouts.
“Twelve months is an equalizer,” Ayoob said. “You hit a wall. Your lifestyle starts to be affected and you get bored. A high dropout rate is a sign that extreme diets can be difficult to maintain. People start to realize they don’t want to avoid their favorite foods, even in small amounts, for a long period.”