Are all Dietary Fats Bad for You?

January 1, 2018

in the 1950s this was the message that resounded in our homes and offices. Ancel Keys, a physiologist, informed the world that dietary fat was responsible for clogging arteries. His landmark study found that people who ate a diet low in saturated fat had a lower incidence of heart disease than those in western countries who ate a fat heavy diet.

Keyes stated that Americans must reduce the fat calories in their diets by a third if they wanted to avoid heart disease. Reducing fat calories also seemed to make sense for weight control since fat contains more calories per gram than protein or carbohydrates. It seemed to make sense that if you reduced the fat calories in yours diet you would not only lose weight but would also minimize the possibility of developing heart disease.

Even though his research and conclusions were flawed, his message went mainstream and became imbedded in modern medicine and nutrition. Almost all of us drank less whole milk. eat less beef, fewer eggs and replaced butter with margarine.


The anti fat message not only went mainstream, but became so embedded in modern medicine and nutrition that it was almost impossible for scientists with contrary opinions to publish research. This began to change when Dr. Walter Willett published the results of a very important study. His team followed the diets and heart health of more than 40,000 middle aged men. They found that if subjects replaced foods high in saturated fats with carbohydrates, there was no reduction in heart disease. Partly because of this study a gradual change began in the way that people thought about fat. An awareness of the importance of monounsaturated and polyunsaturated fats in a healthy diet developed, and the Mediterranean diet became accepted even though it was high in total fat.

How has this changed?  That will be discussed in the next blog.


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Dr. Sanford L. Severin

Dr. Todd D. Severin

San Ramon, CA 94582 USA

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© 2020 by Sanford Severin, MD