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Physical FitnessHigh-confidence evidence for the nutritional value of various amounts of dietary fat
[+8] [5] Jefromi
[2011-10-04 04:29:09]
[ nutrition fat ]
[ http://fitness.stackexchange.com/questions/4100]

Someone said this in a comment to a question on the cooking stackexchange about cooking steak [1]:

The fat is one of the healthier parts of the steak. If you have no fat in your diet, you will die. And grass-fed fats have an ideal balance of omega 6:omega 3 fatty acids, which has been known for decades to reduce the risk of cardiovascular disease.

It seems possibly misleading to me, but I'm by no means an authority. I know fat probably isn't all bad, and one can be quite healthy with plenty of fat in a diet, but it's a bit of a leap from "we need some fat" to "the fat in steak is healthy". I'm also quite aware of how iffy it can be to draw broad dietary conclusions from specific scientific studies, so I'm also suspicious of the claim that because of the ratio of fatty acids, the fat on the whole reduces risk of cardiovascular disease. (Addendum: That is, given that your diet is at the ideal ratio of fatty acids, whatever that is, is there solid evidence that adding more fat at that ratio is a healthy thing?)

So what does our current understanding of nutrition say about amounts of fat (or animal fat) in diets? I'm not looking for answers of the form "a single study found that people who eat more beef fat have a 5% lower chance of a specific form of cardiovascular disease", but rather broader, higher-confidence information, applicable to the general population - even if it's that we can't say for sure whether it's positive or negative on the balance.

"it's a bit of a leap from "we need some fat" to "the fat in steak is healthy" - where's the leap? If fat is needed, don't you need a logical leap to say that it's not healthy? This relates to my comment asking you what you think is unhealthy about fat. It also relates to your comment on Chris Bibbs' answer. If fat is required, what about it are you considering unhealthy? - Dave Liepmann
I will say that dietary fat and body fat are two different things. There is plenty of evidence to say that too much body fat is unhealthy, just as there is to say that too little body fat is also unhealthy. However, eating a pound of dietary fat doesn't put a pound of fat on your body. There are fat born vitamins, although these are more common in fish and milk. Just keep in mind that studies are still being done on the relation of dietary fat to body fat. And regular exercise changes things. - Berin Loritsch
@Berin: I was attempting to ask about dietary fat, and general health, not connection to body fat. - Jefromi
@Dave: The leap is the implicit suggestion that, even if you already have enough fat in your diet, eating additional fat (as long as it's good happy beef fat) will make you healthier. That is, I know eating no fat is bad, and I know eating nothing but fat is bad, but where's the happy medium? How broad is it? - Jefromi
(1) "How broad is it?" can be indirectly answered by how much hard exercise do you do? In short the less sedentary you are the more tolerances your body has to deal with a less than ideal diet. - Berin Loritsch
As the asker of that original question on cooking, I think I should clarify that I wasn't saying that MORE fat is healthy, but that the fat you get from regular consumption of food in your diet is healthy. Especially in the right ratios and from the right sources (as I said in my statement of grass-fed being better). Saying that if you have zero fat in your diet you will die isn't the same as "the more fat you eat the healthier you are," just that having this fat from the steak contributes to healthiness, making it healthy. It need not be inferred that more fat is more healthy. - Bryson
@Bryson: You're still saying that more than "regular consumption of food" is healthy, which is what I was questioning. You can get a pretty good amount of fat from regular meat and dairy. - Jefromi
@Jefromi: My contention is that eating the fat that's a part of the steak is normal, and everybody who's cutting all the fat off is getting LESS than a "normal" amount that you'd get from just eating "regularly". You asked a great question though, I up-voted you and you've got some great answers below. - Bryson
[+10] [2011-10-04 13:34:31] Dave Liepmann

I think that before getting into specific claims, it's important to note that both hypotheses need to be proven in order to be believed. The burden of proof rests on all parties, whether they're proving that dietary fat causes heart disease, or that it doesn't, or whatever other claim they may be making.

Fat Isn't Fattening

The most straightforward research is this: " Dietary fat is not a major determinant of body fat [1]." This has been proven over and over: fat that you eat is just another form of calories. It doesn't make you fat and is perfectly healthy.

Low-Fat Diets Not Proven

Maybe you don't think dietary fat makes one fat, but you still think fat is unhealthy. That's where I recommend reading Taubes [2]: "the low-fat-is-good-health hypothesis has now effectively failed the test of time."

He goes on:

Until the late 70's, the accepted wisdom was that fat and protein protected against overeating by making you sated, and that carbohydrates made you fat. In ''The Physiology of Taste,'' for instance, an 1825 discourse considered among the most famous books ever written about food, the French gastronome Jean Anthelme Brillat-Savarin says that he could easily identify the causes of obesity after 30 years of listening to one ''stout party'' after another proclaiming the joys of bread, rice and (from a ''particularly stout party'') potatoes. Brillat-Savarin described the roots of obesity as a natural predisposition conjuncted with the ''floury and feculent substances which man makes the prime ingredients of his daily nourishment.'' He added that the effects of this fecula -- i.e., ''potatoes, grain or any kind of flour'' -- were seen sooner when sugar was added to the diet.

I am not an expert in the Omega-3/Omega-6 ratio issue, but it suffices to say that A) it's important [3], and B) a modern, processed, grain-heavy, diet is terrible for maintaining a good Omega-3/Omega-6 ratio.

But fat qua fat being a problem is a modern idea, and doesn't seem to have much evidence behind it.

"How Much is Too Much?"

If we are asking "how much fat is OK?" then there are some references. I don't necessarily agree with the science behind this, but one recommendation from the UK's Faculty of Public Health [4] is:

Fats should provide no more than 35% of an individual’s food energy intake (ie. excluding alcohol) – predominantly from poly- and monounsaturated fats. Saturated fats should be limited to no more than 11% of food energy intake. Current average intake of saturated fats is 13.4% for adults and 14.3% for children. WHO recommends reducing trans fats to less than 1% of food energy intake, and ultimately phasing them out altogether.

[1] http://www.ncbi.nlm.nih.gov/pubmed/12566139
[2] http://www.nytimes.com/2002/07/07/magazine/what-if-it-s-all-been-a-big-fat-lie.html?pagewanted=all&src=pm
[3] http://www.ncbi.nlm.nih.gov/pubmed/12442909
[4] http://www.fph.org.uk/uploads/ps_fat.pdf

+1 good answer, I think it answers the core question better than mine. - VPeric
Thanks for the good sources! It seems that your omega-3/omega-6 source suggests that having a good ratio of fatty acid types (i.e. eating the right kinds of fat) is important, but not that your health will be improved by consuming more fat at that ratio. - Jefromi
(1) I agree on the ratio, but would be very interested in any sources which take these points into account that suggest that eating a significant proportion (1/4, 1/3) of one's calories as fat is a problematic practice. I'm just learning this stuff. - Dave Liepmann
@Jefromi It guess it would help if I knew what kind of health problems you expect from eating fat. - Dave Liepmann
@Dave: I don't really have any expectations. If the answer is "between 10% and 40% calories from good fat, overall effect on health is constant within a sizeable error bar" then so be it! - Jefromi
+1 for the China Study link, makes an interesting read - Chris S
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[+5] [2011-10-04 14:40:59] Christopher Bibbs

Yes, certain fats are required for human growth and development. This is a known fact for >40 years.

I'd refer you to Barry Bogin's book Patterns of Human Growth [1]. In chapter 6 Environmental factors influencing growth he covers the research of the 50 essential nutrients as well as the impact of growth and development of different diets from a large sampling of cross-cultural studies.

Barry isn't trying to sell diet books, he's a hardcore researcher so the book is a bit dense, but worth a read to anyone with serious interest in diet and human development.

[1] http://books.google.com/books?hl=en&lr=&id=ScfPjwF3BngC&oi=fnd&pg=PR13&dq=barry%20bogin%20anthropology&ots=gHvXE1UT5Y&sig=ZFNWyybP0wRZ3du4R67P2y50qEk#v=onepage&q&f=false

I know some fat is required; I was more interested in the leap from that to the idea that it's healthy, more is better, and so on. Thanks for the link, though! - Jefromi
(2) The book as a substantial section on the impact of dietary fat on growth and development. It was Barry's primary area of focus when I knew him. Short answer, fats are critical for growth and development of the brain and central nervous system, but it dimishes after that. I think his research is pretty well vetted by now in the scientific community. - Christopher Bibbs
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[+5] [2011-10-04 20:23:20] Joe Blow

For what it's worth Jefromi, I recommend:

Chapter 6 of Life Without Bread Lutz and Allan.

The entirety of Section 1 ("The Fat Cholesterol Hypothesis") of Good calories, bad calories by Gary Taubes.

The entire book The great cholesterol con Malcolm Kendrick (must-read).

And if you prefer Chapters 3 and 4 of the popular The protein power lifeplan by Eades and Eades.

I also strongly recommend the fascinating historic book Eat fat and grow slim by Richard Mackarness.

I actually don't know what you mean, specifically, by "high-confidence" and/or broader proofs or studies, but all of these books (particularly Taubes and Kendrick) are packed with detailed examination of all the relevant major studies, etc.

Essentially, you are probably aware there is currently a major "religious" conflict in medicine/science/government between the "fat is bad for you" camp" and the "don't be ridiculous, fat cannot be bad for you" camp.

I guess, nobody can settle the argument "here and now" but those titles for starters will offer, as I say, particularly the Taubes book, and indeed Kendrick, detailed line-by-line picking-apart of the relevant major studies, and so on. I hope this is relevant to your question.

(A cool soundbite is that your HEART actually runs mainly, perhaps only, on lipides.)


(1) Thanks for all the good suggestions! As for "high-confidence" and "broad"... I envision a spectrum. On one end, there are studies on one end of the spectrum which say that given some set of preconditions (types of diet) a very specific given diet modification (maybe a single chemical component of a food) has some small effect on probability of a specific health issue. On the other end of the spectrum, there are things like the reviews of studies that you mention, and the perfect ideal of large, randomized, long-term trials. For simple advice for general audience, you want the latter. - Jefromi
@Jefromi It's not specifically related to your question, but I recommend reading some of the better debunkings of The China Study. Due to prohibitive cost and logistical issues, the kind of evidence you're looking for is in extremely low supply. The China Study data (but not the book) is a great source of some of the only data of that kind that I'm aware of. - Dave Liepmann
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[+5] [2011-10-04 08:58:41] VPeric

The Eat Like a Predator [1] blog post also suggests favoring meat from grass-fed animals (ruminants), like beef, lamb, venison, goat... -- "Ruminants are far better at converting plants into essential fats, complete protein, and bioavailable nutrients than humans are." There's also a link to this site [2] which summarizes studies on the benefits of eating grass-fed beef. That site lists many, many studies and I don't feel like summarizing all of them; check them out if you are interested. In short, it shows that Omega-3 fats are healthy and that grass-fed animals have more of them, as well as more of other beneficial fats and vitamins.


Bonus question: You will die if you have no fat in your diet: while carbohydrates can be produced by breaking down proteins, the body has no way of producing fat and it has to be a part of your diet. In fact, Eat Like a Predator [3] says:

Frankly, you could stop here, as many native cultures did: as long as you eat organ meats and marrow, fatty, grass-fed ruminant meat provides 100% of your nutritional needs. But most of us enjoy more variety in our diets—and some vegetables and fruits offer tangible health benefits, even if they don’t provide meaningful calories.

[1] http://www.gnolls.org/1141/eat-like-a-predator-not-like-prey-paleo-in-six-easy-steps-a-motivational-guide/
[2] http://www.eatwild.com/healthbenefits.htm
[3] http://www.gnolls.org/1141/eat-like-a-predator-not-like-prey-paleo-in-six-easy-steps-a-motivational-guide/

"Eat Like a Predator" is very focused on advocating rules for a diet, and unproven evolutionary biology reasons for it, and "Eat Wild" provides a lot of the very specific studies that you have to be careful treating as dietary advice. In any case, I'll happily believe that those are the "good" fats, and they're way better for you than the "bad" fats (though I think it could be better demonstrated), but I don't see anything that convinces me that a balanced diet is improved by the addition of "good" fat. - Jefromi
"Traditionally, the Maasai diet consisted of meat, milk, and blood from cattle." Although not surprisingly, that has changed in recent years to include significant grain products. - John C
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[0] [2011-10-10 20:12:32] Chris S

Saturated fat is different from unsaturated fat, and fat found in butter and animal fat is saturated.

(This is somewhat simplified) Fat is simply Carbon, Hydrogen and Oxygen elements combined with glycerol. A molecule of fat contains one molecule of glycerol and three molecules of fatty acids. The fatty acid is a chain of CH groups, and when these are combined with single bonds the fat is said to be saturated.

Here's butyric acid found in butter:

CH3-CH3-CH3-COOH

This only has single bonds, no doubles.

A double bond is mono-unsaturated (commonly Omega 9) fat, and more than one double bond is polyunsaturated. Depending on where the first double bonds lies, these can be Omega 3 or Omega 6 fats.

Below is linoleic acid which you find in a whole host of oils such as sunflower oil, walnut oil:

CH3-CH2-CH2-CH2-CH2-CH=CH-CH2-CH=CH-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH

The "=" is the double bond. In this case it's an Omega 6 as the double bond lies on the 6th CH group.

The evidence supporting the idea that saturated fats lead to high cholesterol and consequently heart disease is huge: here's a small sample of reputable data:

There are strong, consistent, and graded relationships between saturated fat intake, blood cholesterol levels, and the mass occurrence of cardiovascular disease (1) [1]

.

Cardiovascular diseases are associated with lower intakes of green vegetables and higher concentrations of apo-B (a form of so-called bad blood cholesterol) which is associated with increasing intakes of animal protein and decreasing intakes of plant protein.

Western-type diseases, in the aggregate, are highly significantly correlated with increasing concentrations of plasma cholesterol, which are associated in turn with increasing intakes of animal-based foods. (2) [2]

This is in excess (where you consume over 10% of your daily in calories in saturated fat), and animal fats aren't just one type of fatty acid, they contain several. So relating this back to the claim about steaks - yes steak fat does contains some 'good fats'. The fat found in beef contains Linoleic acid and Oleic acid [3], but in very small amounts.

Linoleic is an essential fatty acid which means the body cannot synthesise it. Having said, beef fat is 3% Linoleic acid, so using this as your primary source would be a stupid way of getting the fat.

(1) [4] Wikipedia
(2) [5] China Study Summary by Roger Segelken, via a comment link from Dave Liepmann

[1] http://en.wikipedia.org/wiki/Saturated_fat#Dyslipidemia
[2] http://www.news.cornell.edu/chronicle/01/6.28.01/china_study_ii.html
[3] http://en.wikipedia.org/wiki/Oleic_acid#Health_effects
[4] http://en.wikipedia.org/wiki/Saturated_fat#Dyslipidemia
[5] http://www.news.cornell.edu/chronicle/01/6.28.01/china_study_ii.html

(2) Googling your exact phrase, "saturated fats lead to high cholesterol and consequently heart disease", leads (for me) to a number of sites discrediting and debunking the body of evidence you refer to. I'm no expert and am willing to believe you, but I think you absolutely do need to link to your well-established evidence. A good summary study, as well as a few conclusive studies, would be awesome. - Dave Liepmann
@Dave you're misquoting me. I also said "..However this is in excess". Too much cholesterol: bhf.org.uk/heart-health/conditions/high-cholesterol.aspx Saturated fat nhs.uk/Livewell/Goodfood/Pages/Eat-less-saturated-fat.aspx . I'll try to find some medical studies to back that up, however that's the health service claiming it (they could of course be wrong) - Chris S
I think it's be easier if I just write a bit on LDLs as that is the body of scientific evidence that backs it up, and is found in medical literature (text books). However some googly links: bhf.org.uk/heart-health/prevention/healthy-eating/… nlm.nih.gov/medlineplus/ency/article/002468.htm - Chris S
@Dave the study you have in a comment above seems to give the best evidence, I'll skip the write up of my LDL notes - Chris S
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