(and why you should probably avoid it)
by Dean Esmay
The most common belief about diet in the United States today 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 the medical community, and most especially among popular writers on diet. Consumer advocacy groups, professional medical 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 the danger of dietary fat may be greatly exaggerated. Unbeknownst to the general public, the theory that bad health follows high intake of fats in general or saturated fats in particular has long had its detractors--and the list of detractors has been growing noticeably in recent years.
"The idea that saturated fats cause heart disease is completely wrong, but the statement has been 'published' so many times over the last three or more decades that it is very difficult to convince people otherwise unless they are willing to take the time to read and learn what...produced the anti-saturated fat agenda." (Dr. Mary Enig, Consulting Editor to the Journal of the American College of Nutrition, President of the Maryland Nutritionists Association, and noted lipids researcher.) "Despite abundant evidence that dietary fat bears no relation to development of cancer of the breast, the NIH intends...to try once again to prove a link that is probably not there....Why then does NIH insist on spending $10 million on a study whose hypothesis seems to be little more than wishful thinking? Is it only because of the faddish infatuation with fat as the root of all dietary evil?" (Editorial in NATURE, Vol. 359, 29 October 1992.) "The diet-heart hypothesis [that suggests that high intake of saturated fat and cholesterol causes heart disease] has been repeatedly shown to be wrong, and yet, for complicated reasons of pride, profit and prejudice, the hypothesis continues to be exploited by scientists, fund-raising enterprises, food companies and even governmental agencies. The public is being deceived by the greatest health scam of the century." (Dr. George V. Mann, participating researcher in the Framingham study and author of CORONARY HEART DISEASE: THE DIETARY SENSE AND NONSENSE, Janus Publishing 1993.) "In Framingham, Massachusetts, the more saturated fat one ate, the more cholesterol one ate, the more calories one ate, the lower people's serum cholesterol...we found that the people who ate the most cholesterol, ate the most saturated fat, ate the most calories weighed the least and were the most physically active. (Dr. William Castilli, Director of the Framingham Study. Archives of Internal Medicine, 1992.) "Call it the Big Fat Lie. Fat has, through no real fault of its own, become the great demon of the American dietary scene. It is no myth that one-third of Americans are overweight. It is, however, a myth that Americans are overweight due to excessive fat consumption. (Dr. Richard K. Bernstein, Type I Diabetic and noted diabetic researcher.)Another extremely popular view has long held that the key to weight loss for the chronically overweight is to view fat as the enemy. The popular belief can often be phrased in this simple formulation: "Eating fat makes you fat, eat less fat and you'll be less fat." Although this simplistic view is no longer commonly embraced by most nutritionists, a surprising number of health professionals, personal trainers, and weight-loss gurus continue to make this claim to a public eager to shed its extra pounds.
More conservative dietary authorities stopped making the claim that cutting fat intake would automatically lead to weight loss (or easy weight management) a few years ago. The more conservative low-fat advocates now restrict their claims only to saying that fat has more calories than protein or carbohydrate, and therefore cutting fat is an easy way to cut down on calories without feeling hungry. But there is a significant and growing amount of evidence to question even this more cautious view.
"There is evidence that altering the proportion of the calories in the diet from fat, carbohydrate, and protein can have a limited effect on weight loss; however the effects appear to be quite small." (Methods for Voluntary Weight loss and Control, NIH Technology Assessment Conference Panel, Annals of Internal Medicine June 1992, 116;11)A growing number of authors, most of them medical doctors or people with doctorates in fields such as biology or biochemistry, have recently exploded onto the American diet scene with popular books offering easier weight loss and substantial health benefits from diets higher in fat, higher in protein, and significantly lower in carbohydrate than the popular low-fat diets. Time and more research will probably tell whether the likes of Dr. Robert Atkins, Dr. Barry Sears, Drs. Rachael and Richard Heller, Drs. Mary Dan and Michael R. Eades, and other diet book authors who go against the prevailing views on diet are right or wrong. Nevertheless it's astonishing how frequently and even viciously these people who question the reigning dietary dogma are dismissed, even angrily attacked, by defenders of the low-fat diet. In the meantime, evidence that low-fat diets are by and large ineffective and possibly even dangerous continues to accumulate in some of the world's most prestigious medical journals.
Low-fat diets are ineffective
Low-fat (30% or less total calories daily from fat) diets are generally eaten with a low intake of protein (around 15% is typical) and a very high intake of carbohydrates (60% or more is usually considered "healthy" by low-fat diet gurus).
And yet there is a good deal of evidence that such diets are ineffective for weight loss, may in fact even cause weight gain in some individuals, and that they are completely unnecessary for most individuals seeking to improve their health.
A recent study involving over 40,000 middle-aged and older American men over a period of six years found that there was no link between saturated fat intake and heart disease in men. It also supported the contention that linolenic acid (a form of fat) is preventive against heart disease. (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.) 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) "Even with extreme changes in the fat-carbohydrate ratio (fat energy varied from 0% to 70% of total intake), there was no detectable evidence of significant variation in energy need as a function of percentage fat intake." (Leibel RL. Energy intake required to maintain body weight is not affected by wide variation in diet composition. American Journal of Clinical Nutrition 1992;55;350-5) "We found no evidence of a positive association between total dietary fat intake and the risk of breast cancer. There was no reduction in risk even among women whose energy intake from fat was less than 20 percent of total energy intake. In the context of the Western lifestyle, lowering the total intake of fat in midlife is unlikely to reduce the risk of breast cancer substantially." (Hunter, DJ et. al. Cohort studies of fat intake and the risk of breast cancer - A pooled analysis. New England Journal of Medicine, 334: (6) FEB 8 1996) "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 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.]
At least so far as the risk of heart disease goes, the simple fact is that there is no longer any proof that lowering fat (or cholesterol) intake offers any protection whatsoever against heart disease. This is perhaps best summed up by Drs. Laura A. Corr (Consultant Cardiologist to Guy's and St. Thomas' Hospitals, London U.K.) and M.F. Oliver (of the National Heart and Lung Institute in London, U.K.), in the concluding paragraphs of their recently-published review of all studies to date of low-fat or low-cholesterol diets as a treatment for heart disease:
"The commonly-held belief that the best diet for prevention of coronary heart disease is a low saturated fat, low cholesterol diet is not supported by the available evidence from clinical trials. In primary preventions, such diets do not reduce the risk of myocardial infarction or coronary or all-cause mortality. Cost-benefit analyses of extensive primary prevention programmes, which are at present vigorously supported by governments, health departments, and health educationalists, are urgently required....Similarly, diets focused exclusively on reduction of saturated fats and cholesterol are relatively ineffective for secondary prevention and should be abandoned. There may be other effective diets for secondary prevention of coronary heart disease but these are not yet sufficiently well defined or adequately tested." (European Heart Journal, Volume 18, January 1997.)
Furthermore, despite more than a decade of American diet gurus recommending low-fat diets for weight loss, there remains no study which clearly shows that low-fat diets result in long-term, significant weight loss among the chronically obese. In fact, most such studies show quite marginal improvements in weight, and some actually show significant weight gain among test subjects.
In a two-year study, 171 women on a low-fat diet achieved a maximum weight loss of only about seven and a half pounds at 6 months, and by year two some of that weight was regained. Most significantly, the standard deviation was more than twice the average weight loss, showing that a number of subjects actually gained weight on the low-fat diet, not counting the 13 that dropped out of the program. (Sheppard L et. al. Weight Loss In Women Participating in a Randomized Trial of Low-Fat Diets. American Journal of Clinical Nutrition 1991;54:821-8.).As astonishing as this may sound, it's in no way surprising to those who've spent much time reviewing the scientific literature. The truth is that not one clinical study has ever shown that low-fat diets allow long-term reversal of obesity in most subjects, whether combined with exercise or not. Perhaps most damning of all, 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 hard to jive this fact with claims that lowering fat intake helps those who are overweight to reduce their body fat, or the widespread claim that lowering fat intake makes it possible to eat more food without gaining weight. Some explanations have been offered to continue to support the low-fat paradigm as a workable weight-loss diet, but none are very compelling and none have strong clinical support.
"In the adult US population the prevalence of overweight rose from 25.4% from 1976 to 1980 to 33.3% from 1988 to 1991, a 31% increase. During the same period, average fat intake, adjusted for total calories, dropped from 41.0% to 36.6%, an 11% decrease. Average total daily calorie intake also tended to decrease, from 1,854 kcal to 1,785 kcal (-4%). Men and women had similar trends. Concurrently, there was a dramatic rise in the percentage of the US population consuming low-calorie products, from 19% of the population in 1978 to 76% in 1991. From 1986 to 1991 the prevalence of sedentary lifestyle represented almost 60% of the US population, with no change over time...Reduced fat and calorie intake and frequent use of low-calorie food products have been associated with a paradoxical increase in the prevalence of obesity." (Heini AF; Weinsier RL. Divergent trends in obesity and fat intake patterns: the American paradox.) American Journal of Medicine, 1997 Mar, 102(3):259-64)
(Note: I'm interested in hearing about any scientific literature which DOES support the low-fat diet as an effective weight-loss diet; if you have any please email me at firstname.lastname@example.org ).
Low-fat diets are dangerous
Not only is there a great deal of reason to question the belief that low-fat diets improve health or give significant help in weight loss efforts, but there is a growing amount of evidence that such diets are actually quite unhealthy, raising the risk of heart disease, diabetes, and cancer, not to mention certain psychiatric disorders such as depression and schizophrenia.
A recent American study showed 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). (Jeppeson, J., et. al. Effects of low-fat, high-carbohydrate diets on risk factors for ischemic heart disease in postmenopausal women. American Journal of Clinical Nutrition, 1997;65:1027-33) The largest and most comprehensive study on diet and breast cancer to date, studying over 5,000 women between 1991 and 1994, 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, and that unsaturated fat had a significantly protective effect against breast cancer. (Franceschi S et. al. Intake of macronutrients and risk of breast cancer. Lancet; 347(9012):1351-6 1996) A study involving tens of thousands of American women showed that diets high in carbohydrate (which almost all low-fat diets are) significantly raise women's risk of developing diabetes, although cereal fibre intake seems to have a limited protective effect. (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) High intake of fats from the Omega-3 group increase HDL cholesterol, 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 only 20-30 grams of fat per day. (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. See also Journal of the American College of Nutrition 1991:10(6);593-601) A strong correlation exists between schizophrenia and deficiencies in fats, especially in the n-3 series. Schizophrenics who naturally eat lots of Omega-3 fats tend to have less severe symptoms than those who don't. Supplementation with extra fats in the Omega-3 group significantly improves symptoms of schizophrenia in most patients. Close relatives of schizophrenics show similar deficiencies in Omega-3 fats. 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. (Laugharne JD; Mellor JE; Peet M. Fatty acids and schizophrenia. Lipids, 1996 Mar, 31 Suppl:, S163-5. See also Peet M et. al. Essential fatty acid deficiency in erythrocyte membranes from chronic schizophrenic patients, and the clinical effects of dietary supplementation. Prostaglandins Leukot Essent Fatty Acids, 1996 Aug, 55:1-2, 71-5) "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 Journal of Clinical Nutrition 1995;62:426-33) [note: NIDDM is Non-Insulin Dependent Diabetes Mellitus -- the most common form of diabetes.] Low-fat high-carbohydrate diets eaten by patients with diabetes (NIDDM) have been shown to lead to higher day-long plasma glucose, insulin, triglycerides, and VLDL-TG, among other negative effects. In general, study has demonstrated that multiple risk factors for coronary heart disease are worsened for diabetics who consume the low-fat, high-carbohydrate diet so often recommended to reduce these risks. (Chen YD et. al. Why do low-fat high-carbohydrate diets accentuate postprandial lipemia in patients with NIDDM? Diabetes Care, 1995 Jan, 18:1, 10-6) "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) Numerous studies have shown that high-carbohydrate low-fat diets lead to high triglycerides, elevated serum insulin levels, lower HDL cholesterol levels, and other factors known to raise the risk of coronary artery disease. (See 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. See also 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. See also 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. See also Ginsberg H et. al. Induction of hypertriglyceridemia by a low-fat diet. Journal of Clin Endocrinol Metab, 1976 Apr, 42:4, 729-35)
Is That All?
The references given above do not represent all the evidence against the low-fat diet as a worthless, possibly dangerous, diet. They represent merely a sampling of some of the more relevent studies. Below is some recommended reading for those interested in learning more on the subject.
The simple fact of the matter is that the low-fat diet is a fad diet. Warnings about the dangers of fat in the diet are constant in the media. Fat-phobia is ubiquitous among health-conscious Americans, and a surprising number of people from all walks of life (including most health professionals) continue to recommend a low-fat diet and to preach the "dangers" of fat. Such messages often take on an almost hysterical, or even belligerant, tone. Yet a growing mound of scientific data not only suggests that this diet fad is pointless, but suggests that it may actually be dangerous to the health of millions of Americans and others worldwide.
Recommended Web Sites:
The Low Fat/Low Cholesterol Diet is Ineffective. This is a reprint of the Corr paper mentioned above, as originally published in the European Heart Journal.
Chuck Forsberg's Adiposity 101. This document is a wellspring of useful information. Anyone interested in understanding the current state of obesity research should read this document thoroughly. A good bit of my own work in this document was cribbed directly from Forsberg's work, which provided numerouos useful references and helpful guidance for further research.
An Interview with Mary Enig: [Part 1] [Part 2] [Part 3]. The President of the Maryland Nutritionists Association and a bench chemist with the authorship of numerous scientific papers and many chapters of books on nutrition talks about why the fear of saturated fat is bogus and relates information about what may be the real cause of heart disease, obesity, and other health hazards.
Trans-Fat Info Page. Mary Enig and associate give valuable information refuting many myths about fat and its role in the human diet, and discussing one form of fat they do believe is dangerous: the trans-fatty acids in margarine and other hydrogenated and partially hydrogenated oils.
Low Carb and Ketogenic Diet Resources. The many web pages and other resources referenced here will provide quite a few hours of worthwhile exploration.
I also recommend the following books for popular references on alternatives to the low-fat diets. Diabetics especially are urged to see the Bernstein book.