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 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 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
- 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 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
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.
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.
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’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.
- 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.
- USA Today. March 19, 2007. Page 10B