Best Fats for Fat Burning-The Latest Research
Written by Dan Gwartney, MD
Monday, 12 January 2009
There used to be a saying that “fat is fat.” Dietitians and cardiologists conspired to convince Americans that the growing problem of weight gain was due to “energy-dense” foods. Of the three macronutrients (fat, carbohydrates and protein), fat has the greatest energy density with 9 calories per gram, as opposed to 4 calories per gram for carbohydrates or protein. While it is true, at the most basic level, that someone consuming 500 grams a day of food will gain much more if it is all fat (4,500 calories) as opposed to sugar (2,000 calories), most people do not base their eating on the total mass (grams) consumed.
There are (generally) hedonistic people who eat what they crave; those who mechanically sit down at mealtime and eat what is necessary to get past the social/physical feeding requirement; or compulsive individuals who track total calories, points, carbohydrate grams, etc. [Note: this compulsion can be positive or pathologic depending upon the degree of influence it has on a person’s behavior and psyche.]
In typical, extreme fashion, the American public fled low-fat diets to flock toward the Atkins diet, which is the macronutrient antithesis (opposite) of the low-fat diets. During the induction phase of the Atkins diet, clients are directed to eat a minimal amount of carbohydrates (around 20 grams per day) for a period of approximately two weeks. The diet during this time is predominantly fat (by calorie), yet results in dramatic and rapid weight loss for most who follow the restrictions closely; much of the initial weight lost is water that normally is associated with stored glycogen (sugar) or retained due to the metabolic effects of insulin. Long-term weight loss is as good as or better on low-carbohydrate diets as the low-fat diets provide.1 A number of additional metabolic changes that promote weight loss occur in “low-carb” diets, but that is outside the scope of this article.
As it has become clear that dietary fat is not inherently evil and may even promote better health and weight management, the media has explored the macronutrient class in greater depth. Fat is a very non-specific term, referring in the most basic sense to a large group of chemicals that are composed of a string of carbon molecules ending in an acid terminal (fatty acids). The acid-end is like chemical Velcro that attaches to an alcohol group on the molecule glycerol (along with two other fatty acids) in the storage form, called a triglyceride. To burn fat as a calorie source, the fatty acid is cleaved (separated) from the glycerol molecule by enzymes and broken down in a complex series of reactions in the mitochondria. Fat is a very efficient source of energy, which is why there are so many calories in fat as compared to carbohydrates and protein.
However, as alluded to above, fat is not fat. Scientists have discovered a number of fatty acids, but even the most common (palmitic acid, stearic acid, etc.) are not household names. As with celebrity and politics, some fatty acids have gained a limited amount of public awareness due to media exposure. These include essential fatty acids (EFA) and omega-3 fatty acids. Essential fatty acids are used by the body to create hormone-like molecules; these fats cannot be created by the body, but must be consumed in the diet. EFAs include linolenic acid and linoleic acid; many include oleic acid as an essential fatty acid, as humans can only produce marginal amounts on their own and will become deficient in oleic acid if they are deficient in the other essential fatty acids.
Taking A Look At EFAs
Briefly, let’s look at the EFAs, including the conditional EFA oleic acid. These fatty acids fall in the categories of omega-3, omega-6, and omega-9 (omega 3,6 and 9 respectively). The omega designation refers to the first double bond (a type of chemical bond between two carbon atoms in the fatty acid chain) found, counting from the end opposite from the acid.
Linolenic acid (ALA) is the essential dietary omega-3 fatty acid, found in seed oils and nuts. Flaxseed and hemp are excellent sources of ALA; the acronym ALA refers to the designation alpha linolenic acid, as opposed to gamma-linolenic acid (GLA), which is an omega-6 fatty acid most commonly found in evening primrose oil. Again, ALA cannot be synthesized by the body and must be consumed in the diet. ALA can be incorporated into the membrane of cells, converted into other fatty acids or used for hormone (eicosanoid) production. ALA converts, in part, to EPA and DHA, the omega-3 fatty acids found in fish oil.2
Linoleic acid (LA) is the essential dietary omega-6 fatty acid, found in seed oils but also prevalent in many other food sources.3 People rarely experience a deficiency in omega-6; rather, they tend to have a relative excess of omega-6 to omega-3. Those interested in learning more are directed to read the dated but very informative book Fats That Heal, Fats That Kill by Udo Erasmus.4 Like ALA, LA can be incorporated into cell membranes, converted to other fatty acids (such as the previously mentioned GLA) or used to produce hormone-like molecules. The omega-6 and omega-3 fatty acids compete for some of the same enzyme pathways, so when the balance between omega-6 and omega-3 in the diet is way off, certain conditions are promoted. A diet excessively high in omega-6, particularly arachidonic acid, is suggested to promote inflammation and increase the risk for related conditions.5
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