July 17, 2008

You Ask, I Answer: Battle of the "Diets"

Andy, are you going to blog about [the study that concluded that a low-carb diet was more successful at helping subjects achieve weight loss and healthier blood cholesterol profiles than Mediterranean or low-fat ones]?

-- Anonymous

Via the blog


I was most certainly planning on commenting on this study, mainly because of some very distracting flaws I noticed.

Let's begin with some basic information.

The study -- partially funded by the Robert and Veronica Atkins foundation (potential bias, anyone?) -- took place over 2 years, during which 85% of the 322 participants stuck with their respectively assigned diets (low-fat, Mediterranean, and low-carb.)

Now with some of my "uh, wait a minute" impressions.

Firstly, when it came to weight loss, low-carb beat out low-fat by 4 pounds (10.3 lbs vs 6.3 lbs), but edged out a Mediterranean Diet (which includes higher carbohydrate consumption) only by 0.3 lbs.

And although the low-carb diet resulted in the best blood cholesterol profiles, it's important to note that for this study, researchers "urged [the] dieters [on the low-carb diet] to choose vegetarian sources of fat and protein."

In other words, although the low-carbers had the highest saturated fat intake out of the three groups, the majority of their fats came from plant sources.

There isn't anything groundbreaking here. Anyone keeping up with nutrition research knows that mono and polyunsaturated fats are recommended for heart health.

Hence, this study calls into question the belief so many low-carb fanatics like Gary Taubes fervently hold on to -- that saturated fat is the best for blood cholesterol levels.

The study specifically mentions that the blood cholesterol levels of the low-carbers is due largely to the consumption of monounsaturated fats.

Besides, I always wondered why low-carb enthusiasts even bother bragging about improved cholesterol profiles on their diets when, two seconds later, they turn around and say that the cholesterol-heart disease link is a lie and the result of "bad science." Which is it?

The study wasn't entirely a "low carb diets RULE!" piece, either.

For instance, the Mediterranean Diet -- which was highest in fiber -- proved to be the most effective at managing blood glucose levels.

Yet again, this goes against traditional low-carb beliefs (and, once again, those Gary Taubes loves to pontificate) that the research on fiber is "inconclusive at best" and that there is no need to have it in the diet.

Before anyone jumps down my throat about whether or not I read Good Calories, Bad Calories, Gary Taubes himself said at his New York University talk in March of this year that he didn't think high-fiber grains were any healthier than refined ones.

Speaking of fiber, I noticed that the low-fat group was only asked to consume "low-fat grains."

This struck me as odd, mainly because it is hard to find grains high in fat -- they are all low-fat.

Additionally, it's hard to overlook some bias.

The study does not urge low-fat dieters to consume the healthiest grains (whole grains), yet specifically requests that low-carb dieters eat the healthiest fats.

I also found it strange that for the majority of this study the low-carb group was consuming 120 grams of carbs a day. This is definitely higher than the much lower levels recommended by most low-carb advocates.

Atkins, for instance, usually calls for no more than 100 grams of carbohydrates per day during the maintenance phase.

Finally, take a look at the numbers and you see that although the low-carb group was not calorie-restricted, their caloric intake was lower compared to their pre-study diet.

So, as always, we are talking about weight loss as a result of reduced caloric intake.

15 comments:

Anonymous said...

It's funny how you give a free pass to someone like Marion Nestle, who just repeats the same, tired rhetoric that is representative of the kind of flawed thinking that led us into our current obesity crisis. But when a study comes out that undermines your (and her) arguments, you go over it with a fine-tooth comb, looking for flaws.

Here's a very interesting Wikipedia article that you may want to look at:

http://en.wikipedia.org/wiki/Confirmation_bias

I'll copy the first sentence here:

"In psychology and cognitive science, confirmation bias is a tendency to search for or interpret new information in a way that confirms one's preconceptions and avoids information and interpretations which contradict prior beliefs."

Andy Bellatti said...

Except that this particular study doesn't undermine my argument. In fact, it actually supports "the same, tired rhetoric" you are so critical of. All groups reduced caloric intake and ALL lost weight.

David Brown said...

The Kitava Study sheds light on the low-carb/low-fat debate.

http://www.ajcn.org/cgi/reprint/66/4/845

Andy Bellatti said...

I think it's important to note that just because someone does not agree with low-carb rhetoric does not mean they advocate low-fat diets.

In any case, the Kitava Study pretty much follows RDA guidelines.

These people are getting approximately 2/3 of their calories in the form of carbohydrates. Protein only makes up 10% of their total caloric intake.

Many low-carb advocates love to point out that they have a higher saturated fat consumption compared to current recommendations, completely overlooking the fact that they also have an excellent Omega 3: Omega 6 ratio, which most "Westernized" nations do not.

RicoVado said...

Andy wrote: "Besides, I always wondered why low-carb enthusiasts even bother bragging about improved cholesterol profiles on their diets when, two seconds later, they turn around and say that the cholesterol-heart disease link is a lie and the result of "bad science." Which is it?"

Some low-carbers understand that there is no link between total cholesterol and heart disease, and only a marginal connection between LDL (bad cholesterol) and heart disease (let's bracket the discussion about Pattern B LDL for now).

Some low carbers also understand that there is a link between HDL (good cholesterol) and heart health. And HDL improves with carbohydrate restriction, and fat consumption (saturated, monounsaturated, polyunsaturated).

So there is no contradiction, Andy. Let me know if you need further explanation. And thanks for the fun blog.

Best,
Rico

Andy Bellatti said...

Rico,

What I was pointing out is that for all the fussing that many (and I would say, most) low-carbers do about how cholesterol has nothing to do with heart disease, I find it ironic that they then mention "low carb diets having the best cholesterol profiles." If that specific biomarker means nothing, why bother bragging about it?

Secondly -- HDL can increase as a result of exercise, alcohol, cutting back on trans fats, and increasing monounsaturated fat intake.

Carbohydrate restriction has nothing to do with HDL levels. If anything, certain carbohydrates should be encouraged since soluble fiber (oatmeal, beans, nuts, seeds, fruits, and veggies) can also increase HDL.

David Brown said...

It's important to note that the islanders of the Kitava study were NOT consuming high fructose corn syrup or whole grains. It would be an interesting study to isocalorically substitute whole grains for some of the other carbs consumed by islanders to see what happens to blood values. Of course, we already know what would happen if fructose were added to their diets.

http://www.medicinenet.com/script/main/art.asp?articlekey=82117
http://www.dailycardinal.com/article/667
http://www.sfgate.com/cgi-bin/article.cgi?f=/chronicle/archive/2004/02/18/FDGS24VKMH1.DTL

Andy Bellatti said...

David,

Are you trying to claim that fruit causes obesity? I'm asking because I know many low-carbers see an apple as a "fattening food", which is rather ridiculous considering people from all over the world have been eating fruits for centuries (yes, back when obesity rates were much lower.)

As it is, I eat 2 to 3 pieces of fruit (pure fructose! Oh the horror!) every day and I have yet to become obese.

In fact, my weight is stable... just like my caloric intake. I think I may be on to something here!

David Brown said...

Andy,

By no means am I suggesting that fruit causes obesity. Hey, I eat fruit nearly every day and my BMI is 19. No, the major problem is technologic food additives such as sucrose and high fructose corn syrup.

Several scientists studied the effects of high sucrose intake more than 40 years ago. But funding dried up, partly because experimental evidence of the damaging effects of sucrose alarmed sugar interests funding the research, but mostly because Ancel Keys forced the scientific community to focus on saturated fat as the major culprit in heart disease.

In recent years, saturated fat research by Jeff S. Volek and others coupled with Sugar research by Peter Havel is shifting the focus back to fructose where it should have been in the first place.

Here's an article from Medscape Medical News entitled "Fructose but Not Glucose Consumption linked to Atherogenic Lipid Profile."

http://www.medscape.com/viewarticle/559344

Andy Bellatti said...

Well, yes... sugar is empty calories.

Not at all filling and easy to overeat.

Hence, it is very easy to overeat calories from sugar and, thereby, gain weight.

WifeMomChocoholic said...

Didn't the participants only lose weight for 6 months and then gain some back (on all three diets)? I also read somewhere that they counted the drop-outs' ending weights as their final weights, giving a false impression of maintainance.

Anonymous said...

Taubes comments on the study here:

http://tierneylab.blogs.nytimes.com/2008/07/21/good-news-on-saturated-fat/

Andy Bellatti said...

Thank you for that link.

I like how Gary Taubes comes back to the "saturated fat" argument in regards to a study where the low-carb participants were specifically asked to consume most of their fats from plant sources (UNsaturated fats!).

Why is he using this as a soapbox to talk about how "vilivifed" meat is?

Ugh. I don't know about you, but I'm completely ready for him to fade into obscurity!

Anonymous said...

I don't think that Taubes is going away any time soon. At least, I hope not.

As you may know, the journal Obesity Reviews recently reviewed Good Calories, Bad Calories. The reviewer was Dr. George Bray.

Gary Taubes recently responded to the review. You can read Taubes's response here.

I know you said that you're tired of the whole Taubes thing, but I think that his response is well worth reading, especially for the zinger at the end. Bray just had his clock cleaned, I believe.

I predict that over the next five to ten years, Taubes's ideas will gradually become incorporated into mainstream thinking. He has logic and evidence on his side.

Andy Bellatti said...

Thank you for sharing those links.

I don't think Dr. Bray "had his clock cleaned."

I find it funny how Gary Taubes poses the "puzzle" of how sumo wrestlers gain weight on a low-fat diet. Gee, did he consider that they eat a significant amount of CALORIES?

Gary Taubes reminds me of conspiracy theorists who utilize odd leaps of logic and overlook basic facts in their quest to prove they are right.

I don't think his ideas will gradually become incorporated into mainstream thinking.

There is a part of me that can't help but think that Mr. Taubes continues to push "Good Calories, bad Calories" down everyone's throat at any opportunity because it didn't sell nearly as well as he initially hoped.