Summing It Up
So far in our discussion of fats, we have learned that fats are made up of a substance called glycerol in combination with other substances called fatty acids. We have learned that saturated fats are hard at room temperature, while unsaturated fats are generally liquid at room temperature.
We have seen that unsaturated fats are often called oils. But the term oil can be confusing, because it is also used for substances having no relation to lipids or dietary fats, such as mineral oil or lubricating oil. To keep this clear in your mind, remember that the word oil indicates the physical state of a substance, not its chemical nature.
Adding to the potential confusion is the fact that the hardness or consistency of a fat, which is related to its melting point, can’t be fixed too precisely because fats are generally mixtures rather than pure substances. Dietary fats often contain some of both saturated and unsaturated fatty acids.
Also, the color of a fat has nothing to do with the issue. Animal fats, for example, derive their color from the pigments present in the diet of the animal.
The Difference Between Adipose Tissue And Structural Fat
When we talk about body fat, we differentiate between adipose tissue and structural fat.
Structural fat is the body fat that is essential for the protection of the internal organs, for building parts of the brain, and for the development and maintenance of body cells and hormones.
Adipose tissue is made up mostly of simple fats, while the structural fat is present as more complex lipids, such as phospholipids and cholesterol.
When fats are absorbed through the walls of the small intestines, the glycerol is separated from the fatty acids, and the fatty acids are broken into pieces in the liver. The pieces are known as ketone bodies.
Ketone bodies are used as a source of energy, and like glucose, ketone bodies eventually become carbon dioxide and water. The production of ketone bodies is a part of normal fat metabolism, and it is the way that fat is used.
The amount of ketones formed in the liver depends on the amount of glucose or glycogen (stored glucose) available for use as energy. This reverse ratio means that fewer ketones will be produced in the presence of a lot of glucose. The reason for this is that insulin depresses the formation of ketone bodies. When glucose is being used for energy, ketones are not needed in large amounts. On the other hand, in the absence of adequate insulin, the body metabolizes stored fats to produce the energy that the body’s tissues require.
The action of the pituitary gland on the formation of ketones is just the opposite. Pituitary hormones mobilize fat, and favor the formation of ketones in the liver, thereby decreasing the power of tissues to consume glucose.
What Is Ketosis?
As we have seen in previous articles, when the glucose available for energy use exceeds the tissues’ needs, the glucose, under the influence of insulin, is converted to glycogen and to body fat. But when there are more ketone bodies available for energy use than are needed by the tissues, they cannot be converted into fat storage. They accumulate in the blood, and are excreted in the urine. This is called ketosis.
One of the ketone bodies is called acetone, and it is the chemical that is detected on urine ketone dip sticks.
Ketone production results from the breakdown of body fats. The excretion of the excess ketones in the urine is important because the presence of large amounts of ketone bodies in the blood threatens to upset the acid-alkaline balance of the blood, and thereby, the balance in the tissues.
If you follow a very low carbohydrate diet, and thereby reduce the amount of glucose and insulin circulating in your blood, your body will manufacture increased amounts of ketones, as it uses your stored body fat for its energy needs. In this case, we generally consider the ketosis to be a good thing because excess adipose body fat is being used and discarded.
Some authorities have referred to this kind of ketosis as benign dietary ketosis, or lipolysis ketosis. Lipolysis means fat destruction.
The ketosis controversy stems from the fact that there is another kind of ketosis, more properly called ketoacidosis (keto-ACID-dough-sis). This type of ketosis occurs in serious diabetes, in the total or almost total absence of insulin. It is quite dangerous, and is associated with kidney disease and with certain blood and brain dysfunctions.
Confusion between these two types of ketosis leads some scientists and some doctors to consider all ketosis to be inadvisable. Since the production of ketones can be prevented by the presence of carbohydrates, some consider
the low carbohydrate diet to be dangerous, as well.
In this regard, a very famous phrase was repeated for decades, and is still repeated among those who advocate a high carbohydrate, low fat diet. The phrase is “Fat burns in the fire of carbohydrates.” This means that fat is utilized when carbohydrate is metabolized. But one of the major problems with this viewpoint is the well-known fact that fats are always used by the cells, no matter how abundant – or how meager – the supply of carbohydrates may be.
Fear of ketosis is really fear of ‘fat burning in the weak fire of reduced carbohydrates’. However, readers of these pages have learned that dietary carbohydrates are not required for life, if enough of the proper kinds of protein and fats are eaten.
As we have discussed in previous articles, some of the protein will become glucose, and, additionally, some 10% of the dietary fat will also convert to glucose. This conversion will control the amounts of ketones produced, since the converted glucose will stimulate the release of insulin.
If fat burns in the fire of carbohydrate, the glucose produced by the conversion of the protein and fat will provide enough fire. Consequently, unless there is complete or nearly complete absence of insulin, there will be no ketoacidosis problem arising from the formation of ketones.
If you have not read my series of articles on carbohydrates and protein, you will want to go to the CarbSmart website archives and take a look at them. http://www.carbsmart.com/vital.html
In my next article, I’ll explain how some fats become sugar, and I’ll discuss the fat-related substances known as phospholipids, steroids, and waxes.