How Fats Work

Essential Fatty Acids

The most common fatty acids are found in animal fats and include:

  • Palmitic acid
  • Stearic acid
  • Oleic acid

Your body is able to create these fats whenever it has a caloric surplus. It can create them from straight sugar if there are enough sugar calories coming in (see How Food Works for a discussion of carbohydrates and sugar).


It turns out that there is another class of fatty acids called essential fatty acids that your body cannot manufacture. These fatty acids include:

  • Linoleic acid (LA) (omega-6)
  • Arachidonic acid (AA) (omega-6)
  • Gamma linolenic acid (GLA) (omega-6)
  • Dihomogamma linolenic acid (DGLA) (omega-6)
  • Alpha linolenic acid (LNA) (omega-3)
  • Eicosapentaenoic acid (EPA) (omega-3)
  • Docosahexaenoic acid (DHA) (omega-3)

Because your body cannot manufacture them, they must come in from the food you eat.

Essential fatty acids fall into two groups: omega-3 and omega-6. The 3 and 6 refer to the first carbon double bond position on the fatty acid chain. All essential fatty acids are polyunsaturated, so the 3 and the 6 mean that the first double bond is either 3 or 6 carbons in from the end.

Omega-6 fatty acids are everywhere: corn oil, sunflower oil and soybean oil all contain them. Omega-3 fatty acids are harder to find. Things like flax seeds, pumpkin seeds and walnuts are high in omega-3 fatty acids, as are salmon, trout and tuna. Current thinking is that these two fats need to be balanced in the diet at a ratio like 1-to-1 or 2-to-1, rather than the normal 20-to-1 ratio seen in most Western diets. About the only way to do that is to supplement your diet with omega-3 vegetable oils or to start eating fish in a big way (meaning two or three times a week).

Summarizing all of this information, the current scientific thinking on fat consumption goes something like this:

  • Limit your fat intake to about 30 percent of the total calories you consume. Do not try to cut fat intake altogether, because you do need the essential fatty acids. A gram of fat has nine calories, meaning that if you consume 2,000 calories in a day your total fat intake should hover around (2000 * 30 percent / 9 calories/gram) 67 grams of fat.
  • When consuming fat, try to focus on mono-unsaturated fats like olive oil and canola oil, or on essential fatty acids.
  • When consuming essential fatty acids, try to balance your intake of omega-6 and omega-3 fatty acids. Do that by consuming tuna/salmon/trout or omega-3 oils like flax seed oil.

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