Low-carb diet wins, losers cry foul
The paper that the London Times wrote about last week finally saw publication today in the Journal of the American Medical Association (JAMA). The study showed that a low-carb diet, followed for a year, produced vastly superior weight loss in premenopausal women as compared to a handful of low-fat diets. As might be expected, the promoters of the low-fat diets are crying foul.
The study is pretty straightforward. 311 overweight, premenopausal women were recruited by researchers at Stanford University and randomized into one of four dietary regimens: the Atkins diet, the Zone diet, the LEARN diet or the Ornish diet. After randomization into a specific diet the women received literature and weekly instruction for two months. Researchers obtained blood work, weight and measurements of the subjects at the start of the study and at 2 month, 6 month and 12 month intervals. At the end of the study, those subjects on the Atkins diet lost substantially more weight than subjects on the other three regimens and had either equal or better metabolic findings.
This study is pretty interesting for a couple of reasons. First, the participants were given the books and literature of the various regimes.
Participants were assigned 1 of 4 diet books: Dr Atkins’ New Diet Revolution, Enter the Zone, The LEARNManual for Weight Management, Eat More, Weigh Less by Ornish.
And the one month instruction involved weekly one hour meetings in which the various books were read and studied.
Each diet group attended 1-hour classes led by a registered dietitian once per week for 8 weeks and covered approximately one eighth of their respective books per class. The same dietitian taught all classes to all groups in all 4 cohorts and was rated by participants at the end of the 8-week sessions for enthusiasm and knowledge of the material (rating scale of 1-5, from “strongly disagree” to “strongly agree,” respectively). The LEARN program is intended to be a 16-week program and, therefore, the 8 weeks of guidance through this book reflected an accelerated time frame, which was necessary to match the time frame given for the other 3 diet groups. Efforts to maximize retention in the study included e-mail and telephone reminders for appointments, e-mail or telephone contact from staff between the 2- and 6-month and between the 6- and 12-month data collection points, and incentive payments of $25, $50, and $75 for completing the 2-, 6-, and 12-month data collection, respectively.
The two month instruction period ensured that participants at least read (or had read to them) the book that promoted the particular regimen they were following. Although the participants rated the instructor the same (4.7 out of 5), I can’t imagine that there wasn’t some variation in enthusiasm for a particular program. The same instructor gave instruction to all the groups. How can you get enthusiastic about recommending the Atkins diet then turn around and be just as fired up about hyping Ornish? Or vice versa? I couldn’t do it.
Let’s take a look at what the participants went through in their weekly instruction.
Each group received specific target goals according to the emphasis of the assigned diet. The Atkins group aimed for 20 g/d or less of carbohydrate for “induction” (usually 2-3 months) and 50 g/d or less of carbohydrate for the subsequent “ongoing weight loss” phase. The Zone group’s primary emphasis was a 40%-30%-30% distribution of carbohydrate, protein, and fat, respectively. The LEARN group was instructed to follow a prudent diet that included 55% to 60% energy from carbohydrate and less than 10% energy from saturated fat, caloric restriction, increased exercise, and behavior modification strategies. The primary emphasis for the Ornish group was no more than 10% of energy from fat. Additional recommendations given for physical activity, nutritional supplements, and behavioral strategies were consistent with those presented in each diet book.The guidelines for the Zone and LEARN diets incorporated specific goals for energy restriction, while for the Atkins and Ornish diets, there were no specific energy restriction goals.
So, the subjects were randomized into the various diets, which is important because were they allowed to self-select each would have gravitated to a diet most in sync with his (or her) nutritional beliefs. (Putting someone who would prefer Atkins into the Ornish group and vice versa gives a little more validity to the dropout figures, which, as we’ll see, are enlightening.) And the subjects were given pretty intensive instruction in the particular dietary promoter’s regimen. Not just a generic low-fat diet, for example, but the Ornish low-fat diet as presented by Ornish himself in his own book.
So what happened?
Well, this little graph pretty much says it all.
As you can see, in terms of weight loss the Atkins diet won hands down. The other three contenders were clustered together at a distant second.
Let’s take a look the what the people following the various diets ate in terms of calories and carbs.
If you do the calculations as I did you discover that at the two month mark the subjects on the Atkins diet are eating an average of 1381 kcal per day, 61 grams of which are carbohydrate. The calories and carbs climb throughout the year so that by the end of the study period the Atkins dieters are eating 1599 kcal per day, 140 grams of which are carbohydrate. These carbohydrate figures don’t really fit with the Atkins’ recommendation to restrict carbs to 20 grams per day (the induction phase) for 2-3 months. Were carbs restricted to Atkins levels they would have represented about 5-6 percent of intake instead of the 18-35 percent that it actually turned out.
MD and I are always asked (in fact, she got three emails today alone asking) what is the difference between our diet and the Atkins diet. One of the differences is that we have a different way of counting carbs that allows a more total carb than Atkins, but still provides the same weight loss and metabolic improvement benefits. We discovered by trial and error with ourselves and thousands of patients that insulin can be lowered just fine without the drastic carb restriction the Atkins diet as described in his book demands. In fact the people in this study – although schooled for two months from the Atkins book – were actually on a Protein Power diet, at least for the first two months. (Someday I’ll post on the relationship I had with Atkins and my annoyance that every incarnation of a low-carb diet is referred to as the Atkins diet.)
Here is the complete Table showing the intake of all the macronutrients.
I could drone on forever about all the interesting findings that can be plucked from just this one table, but let me leave you with just two. First, take a look at the fiber intake. I don’t really care about fiber because it’s been shown to be pretty much worthless as any kind of a healthful thing, but others haven’t read all the medical literature yet and so continue to think it’s wonderful. Look at the highest of the high carb diets, the Ornish diet, and notice that there just ain’t that much more fiber than on the Atkins diet. None of the diets has the recommended 25 grams per day. And look at the saturated fat intake. The Atkins diet followers ate a little over 15 percent of their calories as saturated fat (50% more than the recomended 10%), yet they had no increase in LDL. (See chart below). Once again proving that there is really no correlation between saturated fat intake and LDL levels. Finally, I found it interesting that twice as many subjects dropped out of the Zone, Ornish, LEARN diets than did from the Atkins.
The authors of this study drilled down pretty deeply into the lipid levels as a function of fat, especially saturated fat, in the diet.
Many concerns have been expressed that low-carbohydrate weight-loss diets, high in total and saturated fat, will adversely affect blood lipid levels and cardiovascular risk. These concerns have not been substantiated in recent weight-loss diet trials. The recent trials, like the current study, have consistently reported that triglycerides, HDL-C, blood pressure, and measures of insulin resistance either were not significantly different or were more favorable for the very-low-carbohydrate groups. [My italics]
The exception to this pattern has been LDL-C concentrations. Two of the most consistent findings in recent trials of low-carbohydrate vs low-fat diets have been higher LDL-C concentrations and lower triglyceride concentrations in the low-carbohydrate diets. Although a higher LDL-C concentration would appear to be an adverse effect, this may not be the case under these study conditions. The triglyceride-lowering effect of a low-carbohydrate diet leads to an increase in LDL particle size, which is known to decrease LDL atherogenicity. In the current study, at 2 months, mean LDL-C concentrations increased by 2% and mean triglyceride concentrations decreased by 30% in the Atkins group. These findings are consistent with a beneficial increase in LDL particle size, although LDL particle size was not assessed in our study. In addition, we examined non–HDL-C concentrations as an alternate indicator of atherogenic lipoproteins—a variable not substantially influenced by changes in triglyceride concentrations—and observed no significant differences among groups at any time point.
Therefore, we interpret these findings to suggest that there were no adverse effects on the lipid variables for women following the Atkins diet compared with the other diets and, furthermore, no adverse effects were observed on any weight-related variable measured in this study at any time point for the Atkins group. Further examination of the dietary effects on lipid variables would benefit from analyses of lipoprotein particle subfractions and follow-up of longer than 12 months.
Here is the chart of the blood and anthropomorphic findings with all the diets. (I cropped the notes so that the table would fit the page better.)
You can pretty much cruise through these charts and tables yourself and get the gist of the study. The low-carb diet preformed magnificently, as it typically does. Subjects following the low-carb diet lost more weight and had improvement, or at the very least, no change, in all other parameters measured. It was pretty much a grand slam no matter how you count it.
What I have found wonderfully amusing are the anguished cries from those promoters whose diets were savaged in this comparison study. Remember, as you read their comments, that the subjects followed the promoters diets as laid out by the promoters. The subjects on the Dean Ornish diet learned from Dr. Ornish’s book. If they didn’t follow it correctly, who’s fault it that?
From David Katz, who is involved with the LEARN program:
“You lose weight if you have cholera, too,” said Dr. David Katz, director and co-founder of the Yale Prevention Research Center and a longtime critic of the Atkins diet. “You can’t measure overall health by a few cardiac risk factors.” [Is this the same David Katz who says we all need to take statins to lower our cholesterol levels?]
“It’s flawed,” Katz said. [Oh, really? Mind telling me how?]
“Nothing in this study will change nutritional recommendations I make to my patients,” Katz said. [Nothing like an open minded scientist.]
Katz argues that given everything researchers know about food, the debate over the best types of nutrition should be over. People need fresh fruits and vegetables and should stay away from saturated fats and junk food, he said.
He also noted the relatively small amount of weight loss among the women in the study as proof that people need to be exposed to healthy foods at an early age before they gain weight.
“It is sad,” Katz said. “It points out the importance of our overall food environment,” he said.
From Barry Sears:
Barry Sears, creator of the Zone diet, defended his approach to weight loss despite Zone’s fourth place showing in the JAMA study.
He blamed the result on the fact that subjects on his diet in the study group actually ate more carbohydrates and less protein than he recommends in his plan.
The percentage of carbohydrates, proteins and fats subjects consumed in the Atkins group more closely resemble his own recommendation that dieters consume about 40 percent of the calories they take in as carbohydrates, 30 percent in fat and 30 percent in protein. [Go back and look at the charts, Barry]
“I like the term moderation,” Sears said.
The study ”had a good concept and incredibly pathetic execution
And from Dean Ornish:
A new comparison of four diets—including mine—is misleading and riddled with problems.
…many people may go on a diet that harms them based on inaccurate information.
Most study participants weren’t following an Ornish diet, which is 10 percent fat. They reduced their fat intake from an average of 35 percent to only 30 percent after one year. If they’re not following the dietary recommendations, it’s not surprising that they didn’t show as much improvement. By analogy, two thirds of people prescribed Lipitor aren’t taking it only four months later. Lipitor is a very effective way to lower cholesterol levels, but only if you take it. It would have been helpful if the authors had reported findings on the subset of people who actually followed the different diets to see what happened to them.
Dr. Ornish then prattles on about how those who really stick to his diet really do well. Really, they do. It’s tougher to stick to the Ornish diet than it is to discover the father of Anna Nicole Smith’s baby.
As you might imagine, this study won’t put an end to the great diet debate. But those of us who are old hands at the low-carb diet know the answer. It’ll just take the rest of the world a little longer to figure it out.