metabolic standpoint, there appears to be no difference in a ketogenic diet which contains fat and
one which does not contain fat.
The primary reason for the inclusion of dietary fat in the ketogenic diet is to keep caloric
intake high enough to prevent a slowdown of metabolic rate. Recall from chapter 8 that a caloric
deficit below 12 calories per pound of bodyweight can result in the loss of muscle and metabolic
slowdown, both of which dieters want to avoid. Since protein and carbohydrate intake must be
kept relatively constant on a ketogenic diet, the only way to modulate caloric intake is by
changing the amount of dietary fat consumed.
From a practical standpoint, the inclusion of dietary fat tends to promote feelings of
fullness as well as making food taste better, both important aspects of making a diet work for
most people. Those who have tried an all-protein diet can attest to the monotony of consuming
only lean protein at each meal for long periods of time.
In essence, after caloric requirements have been established and protein and carbohydrate
intake set, the remaining calories will come from dietary fat. The details of calculating dietary fat
requirements appear in section 6 where a complete SKD is set up.
An important observation with regards to fat intake is that some individuals have reported
transient stomach upset (and occasionally nausea) when they begin a ketogenic diet, especially if
they have been on a low-fat diet previously. Easing into the ketogenic diet more gradually, by
slowly increasing fat intake and decreasing carb intake at the same time, seems to prevent some
of these symptoms. Additionally, sufficient fiber intake may help.
Quality of fat consumed
Like carbohydrates and protein, fats can be rated in terms of their quality. Much of the
stigma associated with dietary fat is related to fat quality as much as quantity. Almost all of the
dietary fat which we eat on a daily basis is in the form of triglycerides (TG), which is a glycerol
molecule bonded to three free fatty acid (FFA) chains. Depending on the types of FFA present,
TG are typically delineated into unsaturated or saturated.
- Unsaturated fats: Typically speaking, unsaturated fats are found primarily in foods of
vegetable origin such as vegetable oils, nuts and seeds. Unsaturated fats are liquid at room
temperature. Two specific unsaturated fats, called essential fatty acids (EFAs), must be
obtained from the diet as they can not be synthesized within the body. These are linoleic acid
(LA) and alpha-linolenic acid (ALA). LA and ALA occur to some degree in all vegetable source
fats, but the most concentrated sources are flax oil/flax meal, safflower oil, and sunflower oil. - Saturated fats: With only two exceptions (coconut oil and palm kernel oil), saturated fats occur
in foods of animal origin such as the fat in beef or chicken. Dairy fats such as butter and heavy
cream are also sources of saturated fats. Saturated fats are solid at room temperature. - Trans-fatty acids (TFAs): Trans-fatty acids, also called partially hydrogenated vegetable oil,
occur only in processed foods. Food manufacturers bubble hydrogen through vegetable oils to