Weight-Loss Wonders: Is Atkins Best?
Chester J. Zelasko, Ph.D. | March 29, 2007

The results of a year-long study on the efficacy of four different weight-loss programs were recently published in the Journal of the American Medical Association (1). In short order, the CEO of Atkins Nutritionals took out a full-page ad in USA Today to congratulate his employees on helping develop The Atkins Advantage weight-loss products (2). Every company wants to put their best foot forward--there’s nothing wrong with that. But it does raise the question: is the Atkins program really more effective than the other weight-loss programs tested? More importantly, given what we know about statistical significance and clinical significance, do the results have any real-world significance? That’s what this Newsletter discusses.

The Study
The intent of the study was to examine benefits and risks of popular diets, especially those that recommend higher protein intake. Researchers included four diets using the acronym “A TO Z”: the Atkins, a Traditional program, the Ornish, and the Zone.
  • The Atkins focuses on lowering carbohydrate intake, which raises protein and fat intake.
  • The Traditional program used the Lifestyle Exercise Attitudes Relationships and Nutrition (LEARN), the typical diet recommended in the USDA’s Food Guide Pyramid. It’s low in fat and high in carbohydrates.
  • The Ornish is very low in fat and high in carbohydrates.
  • The Zone approach is 40% carbohydrate, 30% protein, and 30% fat.
The subjects were premenopausal women between 25 and 50 years old. The women weighed an average of 187 pounds with an average percent body fat of 40%. The 311 subjects were randomly assigned to one of the four diets and given the popular books that explained the programs. In addition, eight weekly sessions were conducted by a registered dietician to explain each program to the subjects in that group. The researchers attempted to maximize participation by reminding subjects of appointments via phone and e-mail. Subjects were also given incentives to participate by earning money for every testing session throughout the study (at 2, 6, and 12 months.) Dietary intake was assessed by unannounced three-day dietary recalls conducted by telephone.

The Results
The results that attracted the press revolved around weight loss and changes in serum lipids. Subjects in the Atkins group lost more weight after one year than any of the other programs. In addition, there were positive changes in HDL cholesterol, triglycerides, and blood pressure in the Atkins subjects compared to the other programs.

Interestingly, there were no significant differences in total caloric intake between the diet groups either before or after the study. All groups decreased caloric intake by about 300 calories per day after one year. Also, there were no significant changes in exercise habits in any diet group after one year.

The Ad
In the USA Today ad, the Chairman of Atkins made three statements. The first was that the Atkins program was proven to be significantly more effective that the other leading weight-loss programs. The facts: average weight loss after one year for the Atkins was 10.3 lbs, 4.8 lbs. for the LEARN program, 5.7 lbs for the Ornish, and 3.5 lbs for the Zone. While absolutely correct, what the study really revealed was that no program was very effective in helping people lose very much weight in a year. Even with the highest weight loss, the Atkins dieters averaged less than one pound a month; if that’s your goal, there are cheaper and easier ways to get there.

The second statement was that women on the Atkins program lost an average 40% more weight than the women on the next best plan. I think the paragraph above addresses that outcome. While the second statement is absolutely true, it’s still relatively meaningless. Think about it: you spend one year following a weight-loss program and the most you lose is 13.7 ounces per month. Remember also that the subjects got more help than the typical dieter would get: they had eight individual sessions to explain the program and financial incentives to complete the program. If you’re a typical person, all you get is the book. Period.

The final statement was that the women following the Atkins program also experienced the most favorable changes in HDL-cholesterol, triglycerides, and blood pressure. That’s true but interestingly enough, by the end of one year, the carbohydrate intake of those on the Atkins program was double what the plan recommended. In fact, most subjects on average had drifted back toward their original carbohydrate intake in all the programs. This was never addressed by the researchers.

As stated in the opening paragraph, every company should put their best foot forward. It would have been nicer to have a better leg to stand on than the results of this study.

The Problems
There are two problems with the study, and they aren’t really the fault of the researchers or the diets themselves. In order to eliminate skewing the results for any single diet, the subjects were randomly assigned to diet programs. While it’s certainly understandable from a pure research perspective, it probably doomed the study to mediocre weight-loss results. People choose diets because they make sense to them or include foods they may like. Would a vegetarian select an Atkins diet? Unlikely. Would a meat-and-potatoes eater select the Ornish diet? Probably not. In this case, self-selecting the diets would have probably contributed to better results. Nevertheless, the study is meaningful for identifying that as a potential problem for future studies.

The second is a problem that crops up time and time again when dietary recall is used to identify caloric intake of subjects: the calories the subjects claim to have taken in don’t match the results. Examining just the difference in caloric intake before the study began and comparing it with the 12-month caloric intake, the average decrease in calories per day was about 300 calories for each diet. At two months and six months it was even greater. If the subjects had actually been eating what they said they were eating, there should have been at least a 30-pound weight loss after one year in each of the groups instead of the results that were reported. There’s the possibility that the subjects were more sedentary during the study to compensate, but that wasn’t indicated by their reported activity levels. Whether intentional or not, people just don’t report their caloric intake accurately; study after study shows people under-report what they eat and eat larger portion sizes than they think they do. While not specifically addressed in this study, the lack of results shows that’s the case in this study as well.

Bottom Line
Successful weight management can be summed up in just six words: eat less, exercise more, for life. What this study proves is that while weight management is simple in concept, it’s difficult to execute on a daily basis. High-carb, low-carb, high-protein, low-fat, Mediterranean, or vegetarian--the plan you choose doesn’t really matter if you don’t follow it.

It’s like the movie City Slickers when Jack Palance tells Billy Crystal, “You have to find that one thing.” What’s your one thing when it comes to the best diet? It’s whatever will work for you every day for the rest of your life to maintain a lower and healthier weight. Change your lifestyle--change your life.

  1. Gardner, CD, et al. Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women: The A TO Z Weight Loss Study: A Randomized Trial. JAMA. 2007;297:969-977.

  2. USA Today. March 19, 2007. Page 10B
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