What We Know About Fat

Do you think you know which of these is best for you?


What do we really know about fat?  About how fats react in the human body when they are eaten?  Government agencies make a lot of assumptions about fat, and they base that on the popular opinions of physicians and scientists who serve on their advisory committees.  Those recommendations are published, and then are used by many physicians, dieticians, nurses, and other health care professionals as a basis of what to recommend to patients.

But what if those experts got it wrong? When the latest data about fats is examined critically we find out that the recommendations made by those government agencies has no basis in the literature.  However, you will find those recommendations repeated as gospel in almost every website about what to eat and what is healthy for you, even the highly respected websites such as WebMD.com

In the March issue of Nutrition, a highly respected, peer-reviewed, academic publication,  Robert Hoenselaar outlines how the advisory committees not only got their advice wrong, but how they cherry-picked the data (Nutrition 28 (2012) 118-123, Saturated fat and cardiovascular disease: The discrepancy between the scientific literature and dietary advice).

Recommendations from the United States Department of Agriculture (USDA) and European Food Safety Authority (EFSA) regarding consumption of fat are similar

(a) Consume less than 10% of calories from saturated fatty acids by replacing them with monounsaturated and polyunsaturated fatty acids

(b) Keep the intake of saturated fatty acids as low as possible while consuming a nutritionally adequate diet

(c)  Saturated fat intake should be as low as possible

Saturated Fat Monounsaturated Fat Polyunsaturated fat
Butter Corn oil Olive oil
Chicken skin Nuts, seeds Peanut oil/ peanut butter
Most meats Soybean and soybean oil Avocado


In 2003, a meta-analysis of over 50 trials was published examining the relationship of dietary fat to serum cholesterol levels (Mensink RP, Zock PL, Kester AD, Katan MB. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serumlipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr 2003;77:1146–55.).  The conclusion was that saturated fat increases the levels of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) but without changing the ratio of total to the HDL cholesterol.   They concluded that using cholesterol alone as a marker of risk was unreliable. This was because if you replace the saturated fat with carbohydrates or tropical oils if you examine the effects on HDL and apolipoprotein B. They concluded that “… we can never be sure what such fats and oils do to coronary artery disease risk.” To translate that from doctor-scientist language: we can improve some laboratory markers, but really not by any mechanism that makes a difference from what we know.

While a systematic review of randomized trials showed that when saturated fats are replaced by polyunsaturated fats there is a reduction in the laboratory marker for risk of heart disease, there was no association with mortality from heart disease.  To emphasize this: the laboratory values of the patients studied improved, but their mortality didn’t. The review also showed that monounsaturated fat intake significantly increased cardiac events, but no effect from the intake of saturated or polyunsaturated fat. Let me emphasize that: Monounsaturated fats, by at least one study, not only didn’t improve issues with the heart- the patients in that study did worse.


When examining other prospective studies about the risk of saturated fat and cardiovascular disease, there has been a consistent lack of an association between fat intake and heart disease, stroke, or total cardiac events.

Cohort studies show that by replacement of saturated fats with unsaturated fats, or carbohydrates – and examining the hazard ratios for heart attacks and deaths from heart disease were as follows: 0.87 for polyunsaturated fat, 1.19 for monounsaturated fat, and 1.07 for carbohydrates.  For those not familiar with statistics, these are essentially no difference, and if these small statistical numbers are accepted than polyunsaturated fat shows an alarming trend. So here is a study that indicates (with as much precision as most studies these days) that polyunsaturated fats are worse for you than saturated fats.

There is a difference between protection against what we define as risk of heart disease and death from heart disease.  Risk reduction means that we lower the laboratory values of factors we associate with risk – but the end point is death.  In a meta-analysis published in 2010 (Ramsden CE, Hibbeln JR, Majchrzak SF, Davis JM. N-6 fatty acid-specific and mixed polyunsaturated dietary interventions have different effects on CHD risk: a meta-analysis of randomised controlled trials. Br J Nutr 2010;104:1586–600.) examined seven different trials, they found that there was a risk reduction but no change in mortality.  Another study (Skeaff CM, Miller J. Dietary fat and coronary heart disease: summary of evidence from prospective cohort and randomized controlled trials. Ann Nutr Metab 2009;55:173–201.  ) had eight trials found “There is probably no direct relation between total fat intake and risk of CHD (heart disease).
The advise of the USDA is reflected in places like WebMD, recounted in public service commercials, and recited as gospel by health care workers everywhere.  Giving false impressions about what an appropriate diet is.

Many of us constantly look for the right things to eat, the right food to feed ourselves and our families.  For that information we choose what we consider informed sources about risk reduction. What we discover is that there is not a clear answer, at least not yet. The differences between these ingredients are not large enough in the studies performed for a reasonable person to make blanket statements.

The only statements about fat that can be made are that trans-fats are bad for a person.  Trans-fats are the fats found in stick margarine, most pastries, and fast foods – but rapidly being eliminated because of their clearly demonstrated bad effects.

Here is what we do know: eating too many calories, be it of fat, carbohydrates, protein, or alcohol will lead to excess weight, and excess weight is a contributor to heart disease, diabetes, and joint problems.

Eat healthy, fresh, delicious food — all in moderation.

Dr. Terry Simpson About Dr. Terry Simpson
Dr. Terry Simpson received his undergraduate and graduate degrees from the University of Chicago where he spent several years in the Kovler Viral Oncology laboratories doing genetic engineering. He found he liked people more than petri dishes, and received his MD. Dr. Simpson, then became a renowned weight loss surgeon, and a leading advocate of culinary medicine. The first surgeon to become certified in Culinary Medicine, he advocates teaching people to improve their health through their food. On the other side of the world, he has been a leading advocate of changing health care to make it more "relationship based," and his efforts awarded his team the Malcom Baldrige award for healthcare in 2011 for the NUKA system of care in Alaska. A frequent contributor to media outlets discussing health related topics and advances in medicine, he is also a proud dad, husband, author, cook, and surgeon “in that order.” For media inquiries, please visit www.terrysimpson.com.


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