A few of you have undoubtedly already seen this but since some of you are
still talking about fear of fat I thought perhaps this piece that I wrote
recently for the Paleodiet Symposium would help, with a little added
commentary that I put in later for some other folks:
Mime-Version: 1.0
Date: Thu, 15 May 1997 16:14:22 -0400
To: [log in to unmask]
From: Dean Esmay <[log in to unmask]>
Subject: Low-fat diet information
Status:
Commentary:
I'm currently researching a book on the phenomenon of low-carbohydrate
diets and evolutionary nutrition.
As everyone knows, the current dietary view the United States is that
excessive fat in the diet is the primary cause of obesity, heart disease,
and other health problems. This belief is extraordinarily widespread in
both the popular imagination and in much of the health profession,
especially among popular writers on diet. Consumer advocacy groups,
professional health organizations, and government health organizations
almost universally endorse this concept. You can't even listen to stand-up
comics talk about health or fat people without hearing a joke about fatty
foods. The belief that fat is the dietary bad guy is about as close to
universal as any idea in America.
And yet there has long been evidence that diets low in fat and high in
carbohydrate are a potential health hazard to at least some people. In
just the last couple of years, a number of studies have been released
strongly linking diets low in fat and high in carbohydrate with a number of
serious health problems. This is not a generalization or an opinion; these
are peer-reviewed studies in the scientific literature, and/or information
readily available from sources such as the USDA, which can easily be
verified independently by anyone who'd care to. Yet despite the
overwhelming evidence offered in just the past year, few if any of even the
professional organizations have seen fit to acknowledge this problem. In
fact the general reaction to anyone who publicly questions the wisdom of
low-fat diets has been derision or outright attack. (Witness the American
Heart Association's recent "declaration of war" on "fad diets," which is
actually an open attack on any diet which is not a low-fat,
high-carbohydrate diet.)
What all this says about our culture I'm not exactly sure. It seems to me
that once an idea takes hold in the popular imagination, even among
professionals, it is nearly impossible to shake. At times I wonder if
there's any fix for it, or if that's just the way people are.
I wrote a mesage on this subject recently, which I wanted to share. I run a
mailing list for professional researchers in the field of evolution and
human diet (a majority of the members have doctorates in related fields),
and I was asked to post some references regarding the health hazards of
low-fat diets; the references given are by no means comprehensive (I can
supply considerably more to anyone interested), but this is I
think a very good introduction to what's out there in the literature and
just how troublesome the current low-fat diet dogma really is.
Dean
Mime-Version: 1.0
Date: Mon, 12 May 1997 13:30:42 -0400
To: [log in to unmask]
From: Dean Esmay <[log in to unmask]>
Subject: On the subject of fat
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MAA29624
Status:
Regarding fat: I keep hoping we can talk Mary Enig into sharing some of her
wisdom on this subject with us. But in the meantime, here are some
preliminary references to check out regarding the negative and/or
questionable impact of low-fat diets:
-=-
Jeppeson, J., et. al. Effects of low-fat, high-carbohydrate diets on risk
factors for ischemic heart disease in postmenopausal women. Shows that
low-fat, high-carbohydrate diets (15% protein, 60% carbohydrate, 25% fat)
increase risk of heart disease in post-menopausal women over a higher fat,
lower carbohydrate diet (15% protein, 40% carbohydrate, 45% fat).
(American Journal of Clinical Nutrition, 1997;65:1027-33.)
Ascherio A et. al. Dietary fat and risk of coronary heart disease in men:
cohort follow up study in the United States. British Medical Journal, 1996
Jul 13, 313:7049, 84-90. Study strongly suggests no link between fat
intake and heart disease in men and supports the contention that linolenic
acid (a form of fat) is actually preventative against heart disease.
Franceschi S et. al. Intake of macronutrients and risk of breast cancer.
Lancet; 347(9012):1351-6 1996. In the largest and most comprehensive study
on diet and breast cancer to date, studying over 5,000 women between 1991
and 1994, this study showed that women with the lowest intake of dietary
fat had a significantly higher incidence of breast cancer than the women
with the
highest intake of dietary fat. It also found that women with the highest
intake of starch had a significantly higher incidence of breast cancer than
the women with the lowest intake of starch. The study found no evidence
that saturated fat had any effect one way or the other on breast cancer,
but that unsaturated fat had a significantly protective effect against
breast cancer.
Jorge Salmeron et. al. Dietary Fiber, Glycemic Load, and Risk of
Non-insulin-dependent Diabetes Mellitus in Women. Journal of the American
Medical Association. 1997;277:472-477. Abstract has an emphasis on cereal
fibre as a preventative against diabetes, but if you order the complete
study and read carefully the study also fully demonstrates that diets high
in carbohydrate are likely to cause diabetes in women, even independent of
fibre intake, although cereal fibre intake seems to have a protective
effect.
"Our results do not support the recommendation of an isoenergetic high
carbohydrate, low fat diet for improving peripheral insulin action in
adults with glucose intolerance ... the increase in insulin action that we
observed previously with vigorous exercise training was negated when
combined with a diet high in carbohydrates and fiber. ... The subjects in
this study are at increased risk for developing NIDDM" (American Journcal
of Clinical Nutrition 1995;62:426-33) [note: NIDDM is Non-Insulin Dependent
Diabetes Mellitus -- the most common form of diabetes.]
In a study of 171 women on a two year low fat diet, maximum weight loss of
3.2 kilograms [about seven and a half pounds] was reported at 6 months. By
year two some of the weight was regained. The standard deviation was more
than twice the average weight loss, showing that quite a few actually
gained weight on the low-fat diet, not counting the 13 that dropped out of
the program. (American Journal of Clinical Nutrition 1991;54:821-8.)
The average U.S. daily fat consumption is 2.52 ounces, with 10% of males
obese; the average Australian daily fat consumption is much less, but 14%
are obese. (LONGEVITY, May 1992)
Leibel RL. Energy intake required to maintain body weight is not affected
by wide variation in diet composition. Even with extreme changes in the
percentage of energy from fat (0% - 70%) there was no detectable evidence
of significant variation in energy need as a function of percentage fat
intake. (American Journal of Clinical Nutrition 1992;55;350-5) [Meaning:
neither higher nor lower fat intake makes any significant difference for
weight maintenance when calories are constant.]
In the presence of dietary carbohydrate, the preferred fuel is glucose and
the capacity to mobilize fat is limited. Factors that increase blood
glucose during dieting [such as high carbohydrate intake] may stimulate
insulin release and all the metabolic sequelae of circulating insulin.
Fatty acid synthesis is activated and lipolysis is profoundly inhibited by
insulin even at very low concentrations of the hormone. (American Journal
of Clinical Nutrition
1992;56:217S-23S) [Note: Fatty acid synthesis is the creation of body fat.
Lopolysis is the burning of body fat.]
Conventional wisdom holds that low fat diets improve insulin sensitivity.
Unfortunately, this is true only after an ultra-low carbohydrate diet. No
changes in glucose tolerance and substrate oxidation were measured after a
high-carbohydrate low fat diet. In addition, these studies confirm a
growing body of evidence that increasing dietary carbohydrate increases
plasma triglycerides and decreases plasma high-density-lipoprotein (HDL),
increasing the risk of cardiovascular disease. (METABOLISM 1993:42:365-70)
Liu GC; Coulston AM; Reaven GM. Effect of high-carbohydrate-low-fat diets
on plasma glucose, insulin and lipid responses in hypertriglyceridemic
humans. Metabolism, 1983 Aug, 32:8, 750-3. In which it was shown that in
humans with existing trouble with high triglycerides, low-fat
high-carbohydrate diets significantly increased metabolic risk factors for
coronary artery disease.
Coulston AM; Liu GC; Reaven GM. Plasma glucose, insulin and lipid
responses to high-carbohydrate low-fat diets in normal humans. Metabolism,
1983 Jan, 32:1, 52-6. In which it is shown that low-fat, high carbohydrate
diets in normal human males caused changes in insulin, TG, and
HDL-cholesterol concentrations which have been associated with an increase
in incidence of coronary artery disease.
Heller, RF & Heller, RF. Hyperinsulinemic obesity and carbohydrate
addiction: the missing link is the carbohydrate frequency factor. Medical
Hypotheses, 42: 5, 1994 May, 307-12. In which it is suggested that high
carbohydrate diets, especially diets in which carbohydrate intake is
frequent throughout the day, has a strong correlation with obesity, heart
disease, diabetes, and a host of medical problems.
Olefsky JM; Crapo P; Reaven GM. Postprandial plasma triglyceride and
cholesterol responses to a low-fat meal. American Journal of Clinical
Nutrition, 1976 May, 29:5, 535-9. Suggests that low-fat, high-carbohydrate
meals lead to increases in plasma triglyceride levels.
Ginsberg H et. al. Induction of hypertriglyceridemia by a low-fat diet. J
Clin Endocrinol Metab, 1976 Apr, 42:4, 729-35. Shows low-fat
high-carbohydrate diets can induce hypertriglyceridemia.
Franceschini G. et. al. Omega-3 fatty acids selectively raise high-density
lipoprotein 2 levels in healthy volunteers. Metabolism, 1991 Dec, 40:12,
1283-6. Demonstrates that high intake of fats from the Omega-3 group
increase HDL cholesterol levels, which is considered protective against
heart disease. Obviously it would be difficult to eat an Omega-3 rich diet
while following a traditional fat-reduced diet (especially if one were
following one of the popular American diets that has one eating 20-30 grams
of fat per day.) See also Journal of the American College of Nutrition
1991:10(6);593-601.
Laugharne JD; Mellor JE; Peet M. Fatty acids and schizophrenia. Lipids,
1996 Mar, 31 Suppl:, S163-5. Correlation between schizophrenia and
deficiencies in fats from both the n-6 and n-3 series. Supplementation
with extra fats in these groups significantly improved symptoms of
schizophrenia in most patients. Analysis of patients' diet did not suggest
unusual deficiency of fats although subjects who already ate diets with
higher natural intake of n-3 fatty acids showed less severe symptomatology.
The possibility that diets generally low in fat might worsen schizophrenia
or even bring on the condition among those already predisposed to it is
hard to ignore.
-=-=-
Compellingly, despite more than a decade of American diet gurus
recommending low-fat diets for weight loss, there remains no reliable study
which clearly shows that low-fat diets result in long-term weight loss
among the chronically obese. Indeed, according to the USDA, Americans' fat
consumption has consistently gone down over the last 20 or so years while
the American national rates of obesity have gone up at precisely the same
time. Correlation is not causation and yet it is hard to jive this fact with
claims that high-fat diet is the primary cause of obesity. Some
explanations have been offered to continue to support the low-fat paradigm
as a workable weight-loss diet, but none are very compelling. For example,
it has been noted that Americans also increased their daily caloric intake
during this same period of decreased fat intake, which supposedly explains
the differences. And yet the claim of most low-fat diet advocates has been
that lowering fat intake causes people to naturally eat less food.
One hypothesis is that Americans have just somehow, for no apparent reason,
become more piggish and less restrained in their eating habits, although
there is no rational explanation for why this would be, especially in a
period wherein Americans have become more and more conscious of health
issues and striven harder and harder to eat "healthier" (lower fat, lower
cholesterol) diets and to exercise more often. The alternate hypothesis,
that lowering fat intake and raising carbohydrate intake results in higher
insulin levels which results in higher hunger and more difficulty reaching
satiety and higher rates of fat storage has not been well-studied.
How all of this relates to the concept of paleolithic nutrition is hard to
say, but it's quite clear from where I stand that the alleged health
benefit of low-fat diets is becoming increasingly questionable, especially
when such diets are combined with high intake of carbohydrate and low
intake of protein. It seems clear that humans did -not- evolve to eat
high-carbohydrate diets, most especially diets rich in bioavailable
carbohydrate. The best figures I've seen on the mean average intake of
macronutrients (Eaton BS, Konner M, Shostak M. Stone Agers in the Fast
Lane. American Journal of Medicine 1988;84:739-749) show the average
worldwide for hunter/gatherers to be 33% protein, 46% carbohydrate, and 21%
fat, with most of the carbohydrate from high-fibre sources relatively low
on the glycemic index (and thus low in bioavailability). The only
meaningful exception seems to be honey, and just how common honey intake
has historically been around the world seems unclear to me. (Jennie Brand
Miller has had some neat thoughts on that so far but I'm still unclear from
her comments what we can realistically think honey contributed to the diet
of most pre-agricultural peoples.)
There is also the issue that what current hunter/gatherers eat may be
different from what our paleolithic ancestors ate. If megafauna such as
the mammoth was much higher in fat, or if historical humans ate high-fat
organs such as brains, tongues, marrow etc. preferentially to the lean
muscle meat of wild game, fat intake may have been higher than what is
available to most modern hunter/gatherers.
As an individual data point I can say that I know a great number of
chronically obese individuals whose weight and health was massively
improved by drastic lowering of carbohydrate intake and strong increase of
intake of both fat and protein. I happen to be one of those individuals; a
low-fat, high-fibre, high-carbohydrate diet gave me very low HDL
cholesterol, somewhat elevated trigylcerides, and a resting heart rate of
about 92 bpm, despite 60-90 minutes of daily exercise (resistance training
+ aerobics), calorie control, and strictly holding fat intake to very low
levels (20-30 grams per day). Moving to a high-protein, high-fat diet,
even with less exercise and an ad libitum eating pattern (no more calorie
restriction), massively improved my HDL/LDL ratios, dropped my
triglycerides, dropped my resting heart rate by about 15 bpm, and generally
improved my health, not to mention helping me to lose about 25 pounds of
unwanted body fat painlessly.
This experience, along with knowing others with similar experiences, has
naturally led me to be very skeptical of the general wisdom that dietary
fat is a danger to health or a primary cause of obesity. But this also
makes me more likely to be biased on the matter, so of course anything I
have to say on this subject should be taken with a grain of salt.
---
If anyone is interested in further reading on this subject please let me know.
-=-=-
Once in a while you get shown the light/
In the strangest of places if you look at it right ---Robert Hunter
http://www.syndicomm.com/esmay
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