The type of protein ingested should be of high quality from animal products such as red
meat, chicken, fish, eggs and dairy. The nature of the ketogenic diet generally ensures that high
quality protein is consumed unless some type of liquid protein fast is being performed. Some
individuals also choose to use commercial protein powders as a protein source.
Section 4: Fat and the SKD
Having discussed the details of carbohydrate and protein amounts in the last two
chapters, the only remaining macronutrient to be discussed is dietary fat. Although a ketogenic
diet can be constructed with only protein and a small amount of carbohydrate, the caloric intake
is so low that metabolic slowdown will occur. Fat is in essence a caloric ballast, a nutrient which
has a relatively neutral effect on insulin levels or ketosis, and which is used to adjust calories.
What is a fat?
Fats are an organic compound, more accurately referred to as a triglyceride (TG), which is
composed of a glycerol molecule with three free fatty acid (FFA) chains attached. Depending on
the type of FFA chains, fats will vary in their types and effects on the human body. Generally,
TG is subdivided into unsaturated fats, which occur in vegetable oils, and saturated fats, which
occur in animal fats such as butter fat. A third type of TG, called a partially hydrogenated or
trans-fat, is a man-made fat produced by bubbling hydrogen through vegetable oil to make a
semi-solid fat, such as margarine.
Digestion of TG
Regardless of type, all TG is digested the same way: ultimately being broken down into
glycerol and FFA. Depending on a variety of factors, the FFA can be burned for energy by the
muscles or heart, resynthesized back to TG in fat cells, or converted to ketones in the liver. The
glycerol portion of TG can be converted to glucose as discussed in chapter 5.
Cholesterol
Although cholesterol has no direct impact on ketone body formation, confusion about
cholesterol warrants a brief discussion. While not strictly a fat, cholesterol is a compound most
often associated with dietary fat intake.
Cholesterol is a steroid molecule which is used for a variety of functions in the body
including the synthesis of some hormones such as testosterone and estrogen. Cholesterol only
occurs in food of animal origin with an average of 100 milligrams of cholesterol present in 3
ounces of meat.