A new study was just published in the Annals of Internal Medicine testing a low-carb diet against a conventional low-fat one.
Here’s what happened.
Researchers took 307 participants and randomly divided them into two groups.
One went on a low-carb diet, which, let’s face it, was right out of the Atkins playbook. For three months these folks consumed no more than 20 grams a day of carbs from fibrous, low-glycemic vegetables (exactly what the first and rather strict “induction” phase of the Atkins four-stage approach calls for).
For each week after the initial three months, this group then added back in 5 grams per day of carbs. In other words, the first week (after the initial three months) they consumed 25 grams of carbs, the second week 30 grams, and so forth.
Other than carbs, this group had no restrictions and could eat all the protein and fat they wanted.
They kept this up till they reached a desirable weight and were able to stay there.
In other words, standard, textbook Atkins.
The second group went on a standard low-fat diet of between 1200-1800 calories a day. The only “restriction” was to keep fat to 30% or less of calories (standard advice).
The researchers were interested in weight loss, which in research terminology was what was called the “primary outcome”. In other words, weight loss was what they were primarily interested in measuring. (More on that in a moment.)
The results?
There was no difference in weight loss between the two groups.
But don’t think for a minute that’s all there is to this story.
I’m pretty sure the spin-doctors in the conventional media will report this with some variation of “Low-Carb Diet No Better for Weight Loss”.
But—as usual—they will be missing one of the most important parts of the story, or will bury it in the tenth paragraph.
Conventional “Wisdom”?
You may recall that the traditional rap on low-carb diets is that they may work in the short term for weight loss, but “everybody knows” they are dangerous.
So the researchers had a “Secondary Outcome”, meaning there was something else besides weight loss that they wanted to look at—risk factors for heart disease. The ones “everyone knows” are bound to get worse when you follow the Atkins diet (or any other “dangerous” low-carb diet).
Well, um, not exactly.
Six months into the study, the low-carb group had a significantly greater reduction in diastolic blood pressure, a significantly greater reduction in triglycerides and significantly greater reduction in a particularly bad form of “bad” cholesterol called VLDL (very low-density lipoproteins).
And- hold on to your hats—at all time points throughout the 2 years, including at the finish line, the low-carb group had a significant increase in HDL (“good”) cholesterol, approximately 23% increase to be precise.
There’s not a drug on earth that’s been able to do that.
There’s a couple of other things to know about this study.
First, the weight lost by both groups wasn’t enormous- 11 kg in the first year (average for both groups), with both groups regaining some during the second year so that the total weight loss at the end of 2 years (average for both groups) was 7 kg.
This isn’t surprising. Virtually every study I’ve ever seen has found that people start reverting to their old habits to some extent, which is why they gain some weight back. The more they slip back into their old ways, the more they gain back. No surprise there. The individuals who were able to stick with their program gained back the least amount of weight, or even continued to lose weight—the averages don’t tell us that.
Second, you may have noticed that those improved cardiovascular risk factors showed up for the low-carb group (only!) after six months, but that after that, there was no difference between the groups in those risk factors—both had improvements. (Except of course, for the very important improvement in HDL cholesterol, which was seen only in the low-carb group and was sustained throughout the two years!)
That’s not surprising either, and I would consider that likely evidence that the low-carb group started drifting more towards “conventional” eating after six months, thus wiping out the differences between the low-carb and the low-fat group.
So before you buy into the inevitable headlines about how these diets produced identical results, remember that while the weight loss might have been identical, the outcomes were not.
“Averages” often conceal real differences—for example within the low-carb group there were some folks who really stuck to the program, and I’m willing to bet that when the raw data are released, you’ll see a number of individuals who not only maintained their weight (or kept losing) but also maintained the significant gains in cardiovascular risk factors that were dramatically seen after six months.
If you had your choice between two diets- both of which produced weight loss, but one of which did it with less hunger and better cardiovascular outcomes, which would you choose?
Don’t buy for a minute that this study shows “no difference” between low-fat and low-carb. It doesn’t. It showed no difference between groups in the weight loss department, but a significant improvement in cardio risk factors for the low-carb group.
That ain’t exactly chopped liver!
Finally there’s one more thing. All the participants received counseling and support for “behavioral change”. The researchers believe that may be the single most important thing in successful weight loss, even more than which particular diet was followed.
On that issue, they just may be right.
I see this as another argument for why we need to educate people to stop aiming for “weight loss”. When the goal is phrased as “weight loss”, the approaches become superficial and shallow. Instead, if everybody thought in terms of “health improvement”, then people would realize that trying to compare diets based on weight loss numbers has pretty much nothing to do with improving health. People can lose weight by getting sick, by hosting tapeworms in their bodies, by suffering from bulimia or anorexia, and by losing a limb.
Corporate exploitation of people’s desire to “lose weight” has created a huge variety of strange substitutes and pills that remove calories, fats, sugars, etc. from the body at a variety of stages in possibly dangerous ways. Many of these companies spend a lot of marketing dollars to make people to think in terms of “weight loss” instead of “health improvement” because their products do not make people healthier. I don’t know why so many people fell for it for so long.
Weight loss can easily be a symptom of illness rather than health. It’s not useful to judge diets based on weight loss results alone.
It indeed is a shame how these researchers try to weaken the real important results of this study. Emphasizing the behavioral treatment element is about the stupidest thing they could do.
You are right to suspect that things were not equal. The point you may have missed is that the analysis was what is known as intention-to-treat (ITT), which means they included data from the people who dropped out. This is controversial and many serious statisticians think it is nonsense (http://www.JerryDallal.com/LHSP/itt.htm) but in any case a good study will also report the results for those who followed the diet. That the authors didn
Dr. Feinman– as always– offers an insightful analysis with several excellent points, illustrating once again the truth of the maxim “the devil is in the details”. Many thanks, Dr Feinman!
Jb
Dr. Feinman wrote:
[…] This post was mentioned on Twitter by Ryan Lee, Metabolism Society. Metabolism Society said: Which would you choose?; The Diet Wars: The Saga Continues http://bit.ly/bEh2Mb […]
I have never been over weight but never really knew how to eat right. Thats why I read your books. I agree with the
I think it’s also worth highlighting that one was a calorie restricted diet and the other was not. To me this is by far the biggest factor for sustainability of a diet. The “don’t eat crap” diet is much easier to maintain than the “don’t eat” diet.
I read this study a week ago and was thrilled. I have been on a low carb diet for over 5 years now and have never been healthier! I lost 118 lbs and have kept it off! I went from 260 to 142 lbs. I had been overweight all of my life and am so grateful to have, at age 48, found a diet that worked! I had dieted on low fat diets for 30 years and just kept getting bigger!! You can’t tell me that was healthier. Only last weekend I bought a book titled “Living the Low Carb Life” written by Jonny Bowden and now I find a link that is Jonny Bowden talking about the study I read lthe week before. All of the information is very encouraging….maybe people will start to learn that low carb is healthy and sustainable!!
Good analysis Jonny! One thing I’d like to add…
A major problem I always see with a typical “Atkins diet” is that it doesn’t distinguish the types of meats that people are eating, and some people falsely believe this means it’s “healthy” to eat unlimited amounts of grain-fed confinement-raised animal products such as nitrate-laden sausage and bacon and corn-fed beef, instead of healthy animal products such as grass-fed beef and bison, truly free-range eggs, wild fish, game meats, etc.
It would also be smart for anybody on an Atkins style diet to include TONS of raw healthy fat sources like raw nuts and seeds, avocados, coconut, etc.
-Mike
hey johnny, have you read tom naughton’s review of this study? i HIGHLY recommend checking it out:
http://www.fathead-movie.com/index.php/2010/08/19/another-biased-study-maybe/
as you alluded to in your post, the amount of bias that went into this study is unbelievable (even more than usual). the crap that supposed “experts” are able to get away with and spread to the general public fills me with rage
Some people are misinformed about the atkins diet which is why there are a lot of controversies going on. I do agree that an improvement in health does make a huge difference. One shouldn’t go on diets just to lose weight but to be more fit.