Maybe I just can't believe that bacon is health food.

May 29, 2012 7:22 AM

Looking for some critical, reasonably independent discussion of some of the paleo diet claims--does such a thing actually exist? Specifically with regards to cardio exercise and saturated fats/cholesterol.

Specifically, several places I've looked at say things about how cardio exercise is actually bad for you because it increases cortisol levels, and that runners actually have more heart disease than non-runners. Also, the notion that saturated fat and dietary cholesterol are not actually connected to heart disease at all? A lot of it really doesn't sound very unreasonable, but those two things seem to run totally counter to what I knew of previous research, and the reading I've done so far tends to run towards the non-scientific and downright paranoid about the scientific community.

Most of this is just curiosity about stuff like why people take statins if cholesterol isn't what makes a difference, some of it has to do with friends who've gotten kind of fond of this idea recently and some general concern about the long-term health impact in people I care about. I would love to be able to read up on this and actually find something that discusses the scientific evidence on both sides and explains why one should be considered stronger, to help in discussions with people who are taking this up, and maybe make some alterations in my own habits if the way I understand things isn't true.

posted by gracedissolved to health & fitness (16 answers total)

Leangains has some info to get you started.
posted by tayknight at 7:32 AM on May 29, 2012

There was a previous discussion around this here.
posted by Wretch729 at 8:04 AM on May 29, 2012

That is a little more help, taynight, but still demonstrates a few of the specific problems I have, to clarify: It does cite studies, but it doesn't explain why they're relevant or authoritative. Reading just the abstracts, I have no idea why these studies back up what they're cited to support. There's a linked book, but it's self-published. And the author of the blog post isn't exactly trying to objectively evaluate it, although I'm happy to take biased authors if they have more explanation. I don't think any of this means the author's necessarily wrong, but I'm looking for something a bit more concrete and evidence-based.
posted by gracedissolved at 8:16 AM on May 29, 2012

Dig it. I'd like to see more authoritative studies too (since I've lost and continue to use a fair bit of weight on a higher-fat diet than I'd have eaten a few months ago).

Another (completly unauthoritative) link. Heart disease runs in my paternal family. I'd hate to lose weight and die of a heart attack :)
posted by tayknight at 8:28 AM on May 29, 2012

Tangentially related. On the basis of the results of this quantitative assessment, the available epidemiologic evidence does not appear to support an independent association between animal fat intake or animal protein intake and colorectal cancer.
posted by tayknight at 8:40 AM on May 29, 2012

I'd urge you to follow the links in that Leangains article and ask yourself if they appear to say what the author says they say. Berkhan has no credentials and his assertions are extremely questionable.

I very frankly do not take seriously any nutritional or exercise advice that comes out of the body building community because of the single-minded focus on muscle mass gain. The cardio/cortisol/heart disease connection is a good example. It is promulgated almost exclusively in the body-building community. Try and find any substantial epidemiological studies that support it. I've tried to no avail (discounting suggestive but far from conclusive studies of marathon-level runners - if you're not running marathons what's the relevance? An associated note is a lot of this discourse is going on between people for whom extreme exercise is a lifestyle. I'm not going to do strength training for an hour+ daily so advice on how to sustain that is not relevant to me).

There are definitely complicated things going on with dietary fat versus blood lipid levels versus heart disease versus mortality. Personally I just don't think science has gotten to the bottom of it. However I think the "saturated fats don't matter" claims of some in the paleo/body-building community are extremely dubious.

This Harvard SPH article has a lot of research links on the topic of dietary fats, cholesterol etc.

There are definitely studies that suggest simply eliminating saturated fat does not guarantee health benefits. But this might be an issue of specific nutrient-replacement strategies (this gets into the sort of canonical diet blunder of replacing dietary fats with low-fat alternatives that are loaded up with processed simple carbs. At this point pointing that out as a bad idea is not exactly cutting edge nutritional advice). It seems pretty clear that fat choices do matter. And no, bacon is not a health food, and not just because of its lipid profile.

More of the same, but in more of a popular science article (but research angles to follow up if you so desire).

But if you listen to the Paleo community you will find out that the same research means saturated fat doesn't matter, full stop (having said this, I like to read what Guyenet has to say about this stuff, I think he is a little more nuanced).

The bottom line is that I feel like the Paleo people and the Bodybuilding community overemphasize the evidence against the impact of saturated fats, overly ignore the evidence of the benefits of replacing "bad" fats with "good" fats, and generally cherry pick in favor of their core philosophies (the idea of strength uber alles and the idea that 1) we know generally how our paleolithic ancestors ate, 2) that this was a relatively consistent and discreet diet, and 3)that this is the best way to eat today.) The basic principle of Paleo is very disputable. If you haven't explored it the Wikipedia article has some decent input on the back and forth on it.

I don't consider myself any kind of expert, I have a minimal basis in science (undergraduate degree in Chemistry and I work in a scientific field) I'm just trying to figure it out like everybody else. I just can't find the unambiguous conclusions that some people do in the data and find the whole "we evolved to eat saber tooth tigers* so that's what we should eat now" ideology of Paleo a bit pat and narrative. Meanwhile, most of us have so much low-hanging fruit dietary-wise (cutting processed carbs, increasing lower-carb vegetables, increasing beneficial fats), and can embrace a moderate practice of a mix of cardio and strength without any fear of ill effects.
posted by nanojath at 8:55 AM on May 29, 2012 [7 favorites]

*possibly a straw-man representation of the foundations of the Paleo Diet
posted by nanojath at 8:57 AM on May 29, 2012 [1 favorite]

You might find this page of studies behind low-carb diets in general useful. The first section lists studies supporting the lack of causation between consumption of saturated fat and heart disease.

For a more in-depth look at how the lipid hypothesis developed and the major holes in it you should read Gary Taubes' book Good Calories, Bad Calories. He did five years of research for it and it shows.

The exercise cardio thing is a bit more tenuous, but the basic reasoning behind it is that our body is not a closed system, and our consumption and expenditure of energy are not independent variables. That means that if you exercise a lot, you tend to work up an appetite and eat more. Your body also shifts its processes to maintain its weight by becoming more or less efficient at burning energy for fuel. Essentially your body can decide how it wants to partition the energy it receives -- into energy for useful work like running, or to store energy in fat cells. So there's no a priori reason why burning more energy via cardio should make you lose weight. It's still probably good for other reasons though.
posted by peacheater at 8:57 AM on May 29, 2012 [2 favorites]

Last comment, there is a big difference between asserting the evidence in favor of lowering carbohydrate intake as a weight loss strategy versus asserting the claims of the benefits of paleo dieting.
posted by nanojath at 9:08 AM on May 29, 2012

I agree nanojath, and I do feel some of their claims are getting rather farfetched plus not really all that important if you don't get the basics right. But the OP specifically asked about saturated fat and cardio and I think those are both things that paleo and low-carb people mostly agree on, and there's a fair amount of data supporting them.
posted by peacheater at 9:18 AM on May 29, 2012

I believe the running/heart disease issue is restricted to marathon runners.
(The author of that article, Kurt Harris, MD, has a terrific blog at http://www.archevore.com/)

"Paleo" means different things to different people. As a result, it's not as easy to pin down specific health claims compared to well-defined diets like veganism.

Paleo does not necessarily equal low-carb. In fact, there has been a substantial backlash within the paleo community against very-low-carb diets (like, under 25g per day). Same deal with the emphasis on/worship of processed meats like bacon.

The lipid hypothesis, however, gets a lot of skepticism even outside the low-carb echo chamber. Trainer/bodybuilder Anthony Colpo, for example, wrote a book-length takedown of the cholesterol/heart disease hypothesis (I haven't read the book). He's not low-carb and frequently critiques other dogmatic views which he finds among paleo devotees.

Good Calories, Bad Calories is a mixed bag. On the one hand, it presents some very dynamic and readable prose deconstructing how the lipid hypothesis came to dominate the scientific mainstream, and why that hypothesis might be wrong. However, I think Taubes is wrong about carbs/insulin being the sole meaningful factor in obesity and weight loss. That book and its successor (Why We Get Fat) are largely responsible for the low-carb faction of the paleo diet.

The folks who disagree with Taubes (Stephan Guyenet, Paul Jaminet, the aforementioned Kurt Harris, and others) advocate a moderate-carb paleo diet which includes starches from sources like potato, bananas/plantains, tapioca, and even white rice. These same people also tend to be skeptical of processed/cured meats like bacon, even while they endorse other sources of saturated fat like grass-fed beef, butter, coconuts, etc.

The other thing which Taubes is famous for is saying that exercise isn't an effective means for losing weight. I'd be willing to believe it, if only for the fact that sustained weight loss is rare no matter what. However, it's irrelevant, because good cardiovascular fitness reduces mortality regardless of scale weight. If you exercise vigorously and never lose an ounce, you're still probably going to improve your health, improve your insulin sensitivity, and generally increase longevity.
posted by overeducated_alligator at 9:19 AM on May 29, 2012 [4 favorites]

nanojath: The Harvard SPH page is awesome. Thanks.
posted by tayknight at 9:20 AM on May 29, 2012

Tons of good reading material here. I will say that as far as the claims go, I focus on these because they're the ones I've had friends treat as relative gospel--other things seem for some reason to be much more flexible. (Nobody seems to care that much about beans, for example, by comparison.) The Harvard page is very excellent but I've got a lot of things bookmarked for later. Doubt any of it will change anybody's mind, but at least I'll know if I'm missing anything, and not feel like I'm dooming myself to an early grave by cycling.
posted by gracedissolved at 9:56 AM on May 29, 2012

In addition to discussion of fats, you need to look at discussions of carbs (more specifically, grains and starches), as there's more and more evidence that an excess of those are what throw off our metabilism (more issues of diabetes than heart disease), and that the early-20th-century meat-for-dinner approach was better than our low-fat (high-starch/sugar) substitutions have been. I know you asked for sources, and I've been scouring my history to find the two articles that finally put me over the top on this, to some frustration. but I think I finally tracked them down

one was this, although it's not sourced very much. the other was a 10-year-old NYT piece about how the advocation of low-fat diet coincides well with the sharp increase in obesity in the US (unlike many other factors that are often pointed to but more gradual). anyway, may or may not be exactly what you were looking for, but the latter, in particular, was a chewy read.
posted by acm at 11:41 AM on May 29, 2012

Another item which might interest you is this post from Mike Darwin's chronosphere blog:

Interventive Gerontology 1.0: First try to make it to the mean.

Spoiler: he likes the small amount of scientific evidence for the Pritikin Diet and does not care for any of the scientific evidence for any other.
posted by bukvich at 6:31 PM on May 29, 2012

You might find Dr. Peter Attia's writing helpful. He's a distance cyclist who follows a ketogenic diet, and has been doing a lot of research and writing on some of the issues you raise. His recent series of posts examining cholesterol are outstanding.
posted by quivering_fantods at 9:53 PM on May 30, 2012