I'm hesitant to discuss this one, because we don't even have an abstract of a published paper. But since it's going to be bantied about the LC web anyway, I might as well comment on what information we have.
Here's the press release from the conference at which it was presented:
Intermittent, Low-Carbohydrate Diets More Successful Than Standard Dieting, Present Possible Intervention for Breast Cancer Prevention
Here's an article that provides some additional info: Cutting carbs just 2 days a week can spur weight loss
Piecing together the information provided together it appears that they compared weight loss and changes in biomarkers for breast cancer risk in women over a four month period. The diet details are sketchy, but it seems they compared the following diets:
- A 1500 cal/day Mediterranean-style diet, a CRD
- Calorie restricted low carb, 650 cal/day for 2 days per week, "Eat normally" the other 5 days
- Ad libitum VLC (<50g carb/day) for 2 days per week, "Eat normally" the other 5 days
After four months we are provided with the following results:
- Average weight loss for "the intermittent approaches" was 9 lbs vs. about 4 pounds for the CRD. (Not sure why they lumped them together)
- Insulin resistance, IR, reduced by 22% for restricted LC > 14% for “ad lib” LC > 4% for Med-CRD
Low carbers are touting the following statements:
Intermittent, low-carbohydrate diets were superior in lowering blood levels of insulin, which can lead to cancer.
“It is interesting that the diet that only restricts carbohydrates but allows protein and fats is as effective as the calorie-restricted, low-carbohydrate diet,” Harvie said.
At some point I hope to see more responsibility in reporting, especially the more "official" press releases from conferences. Although insulin can promote the growth of cancer cells, I think we need to be very careful what actually "causes" the formation of a cancer cell. I also am getting pretty tired of the equating of normal postprandial insulin production/levels with basal hyperinsulinemia. I think there's enough misplaced paranoia over insulin levels already in low carb circles, and I hope this type of hysteria never goes mainstream. To say that a biomarker associated with increased risk of some disease is a "cause" of that disease is something that should also be stricken from medical reporting. We make no strides if we acknowledge that cholesterol doesn't cause this, that, or the other thing just because LDL has been correlated with increased risk of CVD in too many studies to cite, but can't extend that to insulin. It is the underlying pathology of insulin resistance that is the likely "cause" of the disturbed lipids and the elevated insulin levels.
In the quote from Harvie, she displays some ignorance of how low carb diets really work (when they do), that they lead to significant spontaneous reduction in calories. I would also question the "as effective" qualifier. To me, a 22% reduction in IR vs. a 14% reduction is considerable. If we were going to quantify that in a more sensational ways, we might say that intermittent calorie and carb restriction resulted in 550% greater reduction in IR than the standard diet, while intermittent ad libitum carb restriction resulted in 350% greater reduction in IR. The addition of calorie restriction to the intermittent regime produced a 57% greater reduction in IR. Things like that.
It will be interesting to see what sort of evaluation of actual intake was done in this study. Michelle Harvie has been researching calorie restriction and reduction of breast cancer risk. Indeed another statement in the release will likely be ignored:
“Weight loss and reduced insulin levels are required for breast cancer prevention, but [these levels] are difficult to achieve and maintain with conventional dietary approaches,”
So much for the overweight low carbers who claim LC is inherently healthy. Here is one study from 2009: Biomarkers of Dietary Energy Restriction in Women at Increased Risk of Breast Cancer. In that study, women followed a 864 kcal/d diet for a month (26/62/12 for P/C/F percents). Insulin levels were lowered 32% in that study. There's a confounder here then, as modest weight loss by any means seems to improve these biomarkers.
Let's do a little math. Over 4 months, women on 1500 cal/day lost 4 lbs. Assuming it's all fat (we know it's likely not, but for simplicity's sake lets) that amounts to (4lbs * 3500 cal/lb)÷(4 mo * 30.5 d/mo) ≈ 115 cal/day deficit. Thus we can presume that these women are in energy balance at 1615 cal/day. Thus for the restricted low carbers, consuming only 650 cal/day, they are in 965 cal deficit. Let's do some more math: 2 d/wk * 17 wk * 965 cal/d ÷ 3500 cal/lb = 9.37 lbs. Imagine that. No LC magic.
There's more to this story as well. The LC diet advised was composed of "protein and healthy fats, such as lean meats, olives and nuts". Nothing about fatty meats, tucking butter under the skin of chicken legs, and drinking cream there. Personally, I find that carbs fill me up more after a low carb day. So the ad lib group may have eaten more on LC days than the restricted group, but perhaps ate a bit less on their "normal days" if, indeed, they lost the same amount of weight.
This is yet another study, along with the other Harvie study I cited, demonstrating that "dangerous crash diets" are not so dangerous after all. But this study offers some strategies for folks, and isn't that what it's REALLY all about? Let's face it, a lot of people who want to eat a low carb lifestyle, find they can't stick with it. This leads to binging, falling off the wagon and rebounding, etc. What this study showed was that modest weight loss can be achieved by "crashing" for only 2 days per week. It's not specified if these were sequential or spaced throughout the week. I know I do very well spontaneously eating not a whole lot when I eat like Jessica Biel (only I prefer tuna over salad to skinless chicken breasts), but it's not all that enticing for too long. Imagine if these women had eaten a mildly restricted "normal diet" on the other 5 days, or done the LC for 3 days per week. The weight loss wasn't fast, that's for sure. But if it continued? That's changing habits for 2 days per week to lose roughly 25 lbs in a year.
Is this study an ultimate boast for LC? Perhaps. But what sort of LC? The improvement in insulin resistance was considerable when caloric restriction was coupled with low carb. The improvement in IR was seen for people eating high carbs the other 5 days of the week. The improvements were seen for LC *in caloric deficit* (intentional or otherwise) with accompanying weight loss, assessed after the weight loss.
I think this study is ultimately a feather in the cap for the intermittent fasters. Coupled with other "crash diet" results, it seems to me that IR in the overweight/obese is a product of overnutrition. Merely draining the tanks occasionally seems to produce marked improvements. Since non-oxidative glucose disposal is the pathway most often identified "defective" for those with IR (as measured by impaired clearance of glucose from circulation), periodically draining not only the general fuel tank, but specifically the glycogen storage tank makes sense -- common sense -- to me as a strategy for metabolic health.
An interesting followup would be what happens in the long run with this approach. After a year, do they continue to lose? Do the metabolic biomarker improvements persist if/when weight levels off? Is there any benefit to intermittent low carbing without accompanying weight loss (I think perhaps, attributed to cyclic depletion of glycogen).
EDIT: A charity that supports Harvie's work had more information on their blog:
The results of the study produced effective weight loss results, with an average loss of six kilograms (13.2 pounds). Similar results were produced by women following the normal daily calorie restricted diet; the findings are important because they could give people who are overweight an alternative way to lose weight.
The intermittent diet provided the women with 650 calories (kcal) in the form of two pints of semi-skimmed milk, four portions of vegetables (80g/portion), one portion of fruit, a salty low calorie drink and a multivitamin and mineral supplement.
As OnePointFive notes in the comments, they don't even mention the ad libitum low carb arm of lean meats. I'd also point out that the data are different than what was presented at the conference. The 13.2 lbs is more than the 9 lbs ... and now they say the results were similar?? Don't know what to make of this. I would also take issue with the characterization of that 650 cal/day diet as low carb in the classic sense. Sure, it's LC because it's so low in calories, but two pints (1 quart) of "semi-skimmed milk" -- likely 1% -- contains 415 calories, 51g carb, 9g fat and 33g protein which works out to 49%C / 20%F / 31%P. The fruit & veggies would add more carb mostly so this could just as easily been called an intermittent very low fat diet.
I'm still curious to see if this study involved some quantification of what was actually eaten by at least a few self-report 24 hour recalls.