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.)
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.
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.