Tuesday, April 1, 2008

Low-carb Review Article

The other day, I came across this nice review article from the American Journal of Clinical Nutrition. It gives a thorough but accessible overview of the current state of research into carbohydrate-restricted diets, without all the fatophobic mumbo-jumbo. It points out a few "elephants in the room" that the mainstream likes to ignore. First of all, the current approach isn't working:
The persistence of an epidemic of obesity and type 2 diabetes suggests that new nutritional strategies are needed if the epidemic is to be overcome.
They claim that preagricultural diets were low in carbohydrate:
In contrast to current Western diets, the traditional diets of many preagricultural peoples were relatively low in carbohydrate (1, 2). In North America, for example, the traditional diet of many First Nations peoples of Canada before European migration comprised fish, meat, wild plants, and berries. The change in lifestyle of several North American aboriginal populations occurred as recently as the late 1800s, and the numerous ensuing health problems were extensively documented (3-5). Whereas many aspects of lifestyle were altered with modernization, these researchers suspected that the health problems came from the change in nutrition—specifically, the introduction of sugar and flour.
But of course, many of them were very high in carbohydrate, and these cultures seemed in fine health as well.

Carbohydrate reduction leads to a normalization of appetite:
It may also be that the mere lowering of serum insulin concentrations, as is seen with LCDs, may lead to a reduction in appetite. In support of this idea, several studies have found that insulin increases food intake, that foods with high insulin responses are less satiating, and that suppression of insulin with octreotide leads to weight loss (27-29).
I can't believe it; all that fat isn't going to clog my arteries??
Several outpatient diet studies have shown reductions in CVD risk factors after an 8–12-wk LCKD, during weight loss, and during weight maintenance (21, 60-62).
The last paragraph is a zinger:
We emphasize that strategies based on carbohydrate restriction have continued to fulfill their promise in relation to weight loss and that, contrary to early concerns, they have a generally beneficial effect on most markers of CVD, even in the absence of weight loss. In combination with the intuitive and established efficacy in relation to glycemic control in diabetics, some form of LCD may be the preferred choice for weight reduction as well as for general health.


Anonymous said...

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. said...

I'm just waiting for Stephan to write ... Ha Ha! I got you! April Fools - There is no such report!

Stephan Guyenet said...

Haha... no such luck, fatophobes

Anonymous said...

Well, it's not like the American Journal of Clinical Nutrition is exactly a hotbed of Ornish supporters. They've been publishing studies showing benefits of low-carb for quite some time. I just wish professional nutritionists actually, you know, read it.

Stephan Guyenet said...

I figured the AJCN must be low-carb friendly since the review was partly funded by the Atkins foundation.

Debs said...

It's a shame mainstream nutrition folks won't bother reading something that contradicts "conventional wisdom." The ability to question commonly held beliefs seems pretty integral to science.

Anyway, it's nice to have another good reference on this stuff.

Mike said...

Whoa, is that really a problem? Why would someone go into nutrition with that attitude? Maybe I'm naive, I've only recently started caring about diet and health.

I pretty much think conventional wisdom can kiss my a$$.

Anonymous said...

Shoot. I'm sorry to hear it was funded by the Atkins foundation. I was sort of hoping it was someone who didn't have a dog in the fight, if you know what I mean.

Stephan Guyenet said...

I agree, that aspect is disappointing. It's still a good review though. It even discusses potential negative side effects.

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Unknown said...

Okay, so I'm over 5 years late to this discussion, but I only just found your blog through Peter's Hyperlipid blog.

One gem in the review article was this:
The investigators wrote, “After 14 d on this [0% carbohydrate, 11% protein, and 89% fat] diet, 3 h of hyperinsulinemia were not sufficient to suppress fat oxidation and increase glucose oxidation. ...”

That statement kinda shocked me. I've been reading a lot of Peter's Hyperlipid blog (and Peter Attia's blog), and I've always had this impression that carbs can easily knock even a keto-adapted person out of ketosis, unless they have a decent glycogen debt (e.g., after exercise). And the culprit that Dr. Attia pins the blame on is insulin.

So I find it fascinating that this study found 3 hours of elevated insulin to be "safe". Maybe the test subjects dropped out of ketosis (I'll have to read the study and see if it was even measured), but at least they were still preferentially burning fat instead of glucose.

The link for the study in question is here, if anyone (like myself) wants to follow up: