There are two levels on which dietary fats can be considered. The first and most basic level is about general health. Certain fats are “essential” because the body can not make them from scratch, and their deficiency leads to illness. In general, in the US we do not get enough omega-3s in our daily diet. This is due to 3 reasons, 1) the food industry has made food products that aren’t nutritionally complete, 2) the dairy industry has changed the way they raise animals leading to less nutritious dairy products, and 3) most people in the US don’t eat enough foods with omega-3s in them.
The result is too many vegetable fats, saturated fats, and trans-fats. Adding omega-3s in the form of fish oil seems to be the simplest way to significantly improve the ratio of essential fats in our diet. Using flax oil is another option, though the results are less predictable due to interindividual differences in fat metabolism.
There are a number of fatty acid supplements you can find in the stores. Many of them are based on a mixture of essential fats to provide the right balance. This is a good idea in theory, unfortunately, in order for the supplements to really impact fatty acid imbalances; you would have to abstain from all other fats in the diet.
A better, or more efficient, solution is simply to add those fats you lack, namely omega-3s. This is why fish oil is such a great supplement.
CLA also has health benefits, particularly against certain types of cancer.
The other level which fatty acids can be considered is from a physiological stand point, namely as body composition modulators. Certain fats, when they are stored within fat cells, alter fatty acid metabolism when they are metabolized in the fat cell. Two such fats with this property are fish oil (EPA) and CLA. EPA form fish oil makes a fat cell fat resistant, and enhances its ability to mobilize stored fat. Fish oil can also increase insulin sensitivity. CLA also acts in the same way as fish oil, but it also appears to act as a PPAR-gamma antagonist. Or at least the 10:12 isomer. The 9:11 isomer appears to be a PPAR-alpha agonist, which also has benefits once inside the fat cell. You can read more about PPAR-gamma antagonists here (Expert Opin Investig Drugs. 2003 Apr;12(4):713-6.)
The jury is still out among academics with respect to CLA. It has many effects in the body. I personally recommend (and use myself) a reasonable intake of CLA (2-6 grams per day) based on the current data.
So, in summary, fish oil provides essential fatty acids that are normally deficient in most people who do not consumer a lot of sea food. CAL also has basic health properties. Both fish oil and CLA have the ability to alter body composition by modulating fat metabolism once stored in fat cells. Finally, taking supplements which only contain those fatty acids that are missing in the diet, rather than blends which provide all fatty acids, is a more efficient way of getting your fatty acid intake balanced.
